Australian/New Zealand Standard · AS/NZS 3008.1.1:2009 This Joint Australian/New Zealand Standard was prepared by Joint Technical Committee EL-001, Wiring Rules. It was approved

AS/NZS 3008.1.1:2009 (Incorporating Amendment No. 1)

Australian/New Zealand Standard™

Electrical installations—Selection of cables

Part 1.1: Cables for alternating voltages up to and including 0.6/1 kV—Typical Australian installation conditions

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AS/NZS 3008.1.1:2009

This Joint Australian/New Zealand Standard was prepared by Joint Technical Committee EL-001, Wiring Rules. It was approved on behalf of the Council of Standards Australia on 14 September 2009 and on behalf of the Council of Standards New Zealand on 2 October 2009. This Standard was published on 26 October 2009.

The following are represented on Committee EL-001:

Association of Consulting Engineers Australia

Australian Building Codes Board

Australian Industry Group

Communications, Electrical and Plumbing Union

Consumers’ Federation of Australia

Electrical and Communications Association (Qld)

Electrical Contractors Association of New Zealand

Electrical Regulatory Authorities Council

Electrical Safety Organisation (New Zealand)

ElectroComms & Energy Utilities Industries Skills Council

Energy Networks Australia

Institute of Electrical Inspectors

Ministry of Economic Development (New Zealand)

National Electrical and Communications Association

New Zealand Council of Elders

New Zealand Electrical Institute

Telstra Corporation Limited

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This Standard was issued in draft form for comment as DR 06745.

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AS/NZS 3008.1.1:2009 (Incorporating Amendment No. 1)

Australian/New Zealand Standard™



COPYRIGHT

© Standards Australia Limited/Standards New Zealand

All rights are reserved. No part of this work may be reproduced or copied in any form or by

any means, electronic or mechanical, including photocopying, without the written

permission of the publisher, unless otherwise permitted under the Copyright Act 1968

(Australia) or the Copyright Act 1994 (New Zealand).

Jointly published by SAI Global Limited under licence from Standards Australia Limited,

GPO Box 476, Sydney, NSW 2001 and by Standards New Zealand, Private Bag 2439,

Wellington 6140

ISBN 0 7337 9274 X

Originated in Australia as AS 3008.1—1984.

Second edition 1989. Jointly revised and redesignated AS/NZS 3008.1.1:1998. Fourth edition 2009.

Reissued incorporating Amendment No. 1 (August 2011).

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AS/NZS 3008.1.1:2009 2

PREFACE

This Standard was prepared by the Joint Standards Australia /Standards New Zealand Committee EL-001, Wiring Rules, to supersede AS/NZS 3008.1.1:1998, Electrical

installations—Selection of cables, Part 1.1 Cables for alternating voltages up to and

including 0.6/1 kV—Typical Australian installation conditions.

This Standard incorporates Amendment No. 1 (August 2011). The changes required by the

Amendment are indicated in the text by a marginal bar and amendment number against the

clause, note, table, figure or part thereof affected.

This Standard is applicable to Australian installation conditions where the nominal ambient air and soil temperatures are 40°C and 25°C, respectively. Part 1.2 is applicable to New Zealand installation conditions where the nominal air and soil temperatures are 30°C and 15°C respectively. Each Part is a complete Standard and requires no reference to the other.

Part 2 will deal with cables for use with alternating voltages over 1 kV.

The objective of the Standard is to specify current-carrying capacity, voltage drop and short-circuit temperature rise of cables, to provide a method of selection for those types of electric cables and methods of installation that are in common use at working voltages up to and including 0.6/1 kV at 50 Hz a.c.

This Standard differs from the 1998 edition as follows:

(a) The limitations of the installation of thermoplastic insulated cables have been further clarified.

(b) An explanation has been provided regarding the properties of cross-linked materials at higher temperatures.

(c) Information has been included on the effect of harmonic currents on balanced three-phase systems, the effect of parallel cables and the effect of electromagnetic interference.

(d) Ratings for cables with flexible conductors and cables exposed to the sun have been extended in the tables of current-carrying capacities.

(e) Thermoplastic insulated cables with temperature ratings of 90°C and 105°C have been included in the tables covering current-carrying capacities of cables with 90°C rated cross-linked insulation materials.

(f) For cables with conductor sizes up to 10 mm2 the values of current-carrying capacities for installation in underground wiring enclosures have also been used for the situation of installations ‘buried direct’.

(g) Current-carrying capacities for cables installed in wiring enclosures have been recalculated according to IEC 60287.

(h) The values for all current-carrying capacities have been expressed to the nearest ampere to align with current IEC practice.

(i) Additional values for a.c. resistance and three-phase voltage drop have been included for single-core aerial cables with bare or insulated conductors operating at a conductor temperature of 80°C.

(j) Table headings have been simplified and now listed in an Appendix for ease of reference.

In the preparation of this Standard, reference was made to IEC 60287 and acknowledgment is made of the assistance received from that source.

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Statements expressed in mandatory terms in notes to tables and figures are deemed to be requirements of this Standard.

The term ‘informative’ has been used in this Standard to define the application of the appendix to which it applies. An ‘informative’ appendix is only for information and guidance.

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CONTENTS

Page

SECTION 1 SCOPE AND APPLICATION 1.1 SCOPE ......................................................................................................................... 6 1.2 APPLICATION ........................................................................................................... 6 1.3 ALTERNATIVE SPECIFICATIONS .......................................................................... 7 1.4 REFERENCED AND RELATED DOCUMENTS ....................................................... 7 1.5 DEFINITIONS ............................................................................................................. 8

SECTION 2 CABLE SELECTION PROCEDURE 2.1 GENERAL ................................................................................................................. 10 2.2 SELECTION PROCESS ............................................................................................ 10 2.3 DETERMINATION OF MINIMUM CABLE SIZE BASED ON CURRENT-

CARRYING CAPACITY CONSIDERATIONS........................................................ 10 2.4 DETERMINATION OF MINIMUM CABLE SIZE BASED ON VOLTAGE DROP

CONSIDERATIONS ................................................................................................. 11 2.5 DETERMINATION OF MINIMUM CABLE SIZE BASED ON THE

SHORT-CIRCUIT TEMPERATURE CONSIDERATIONS ..................................... 12

SECTION 3 CURRENT-CARRYING CAPACITY 3.1 RATINGS .................................................................................................................. 13 3.2 TYPES OF CONDUCTORS ...................................................................................... 13 3.3 TYPES OF CABLE ................................................................................................... 15 3.4 INSTALLATION CONDITIONS .............................................................................. 16 3.5 EXTERNAL INFLUENCES ON CABLES ............................................................... 20

SECTION 4 VOLTAGE DROP 4.1 GENERAL ................................................................................................................. 86 4.2 DETERMINATION OF VOLTAGE DROP FROM MILLIVOLTS PER AMPERE

METRE ...................................................................................................................... 86 4.3 DETERMINATION OF VOLTAGE DROP FROM CIRCUIT IMPEDANCE .......... 87 4.4 DETERMINATION OF VOLTAGE DROP FROM CABLE OPERATING

TEMPERATURE ...................................................................................................... 88 4.5 DETERMINATION OF VOLTAGE DROP FROM LOAD POWER FACTOR ........ 89 4.6 DETERMINATION OF VOLTAGE DROP IN UNBALANCED MULTIPHASE

CIRCUITS ................................................................................................................. 90

SECTION 5 SHORT-CIRCUIT PERFORMANCE 5.1 GENERAL ............................................................................................................... 113 5.2 FACTORS GOVERNING THE APPLICATION OF THE TEMPERATURE

LIMITS .................................................................................................................... 113 5.3 CALCULATION OF PERMISSIBLE SHORT-CIRCUIT CURRENTS .................. 114 5.4 INFLUENCE OF METHOD OF INSTALLATION ................................................. 115 5.5 MAXIMUM PERMISSIBLE SHORT-CIRCUIT TEMPERATURES ..................... 115

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APPENDICES A EXAMPLES OF THE SELECTION OF CABLES TO SATISFY

CURRENT-CARRYING CAPACITY, VOLTAGE DROP AND SHORT-CIRCUIT PERFORMANCE REQUIREMENTS ....................................... 117

B LIST OF TABLES ................................................................................................... 126 C EXAMPLES OF THE APPLICATION OF REDUCTION FACTORS FOR

HARMONIC CURRENTS ...................................................................................... 130 D RECOMMENDED CIRCUIT CONFIGURATIONS FOR THE INSTALLATION

OF SINGLE-CORE CABLES IN PARALLEL ........................................................ 131

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STANDARDS AUSTRALIA/STANDARDS NEW ZEALAND

Australian/New Zealand Standard



S E C T I O N 1 S C O P E A N D A P P L I C A T I O N

1.1 SCOPE

This Standard sets out a method for cable selection for those types of electrical cables and methods of installation that are in common use at working voltages up to and including 0.6/1 kV at 50 Hz a.c.

Three criteria are given for cable selection, as follows:

(a) Current-carrying capacity.

(b) Voltage drop.

(c) Short-circuit temperature rise.

This Standard provides sustained current-carrying capacities and voltage drop values for those types of electrical cable and installation practices in common use in Australia. A significant amount of explanatory material is also provided on the application of rating factors that arise from the particular installation conditions of a single circuit or groups of circuits. Also, provided in Section 5 is information on cable selection based on short-circuit temperature limits.

NOTE: A number of worked examples on cable selection are included in Appendix A.

This Standard does not take into account the effects that may occur owing to temperature rise at the terminals of equipment and reference is necessary to AS/NZS 3000 and the individual equipment Standards.

NOTE: For ease of reference, an index of the Tables included in this Standard is provided in

Appendix B.

1.2 APPLICATION

This Standard is intended to apply to installations made or carried out after the date of publication, but it is recommended that it not be applied on a mandatory basis until 6 months after the date of publication. However, if work on an installation commenced before publication of this edition, the inspecting authority may grant permission for the installation to be carried out in accordance with the superseded edition.

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1.3 ALTERNATIVE SPECIFICATIONS

AS/NZS 3000 gives current-carrying capacities for a limited number of cable installation conditions. These conditions are included in this Standard but, in some cases, where recalculations have been performed, the tabulated values differ slightly between the Standards. Where this occurs the current-carrying capacity given in this Standard is considered to be more accurate, but either value is acceptable for the application of any appropriate requirements of AS/NZS 3000, e.g. maximum current rating of a circuit-protective device.

Where the type of cable or method of installation is not specifically covered in the tables of this Standard, current-carrying capacities obtained from alternative specifications such as ERA Report 69.30 may be employed.

ERA Report 69.30, particularly Part III, gives information on the following areas that are not covered by this Standard:

(a) The d.c. current-carrying capacities of two single-core cables and one two-core cable.

(b) The current-carrying capacity of armoured single-core cables.

(c) Group rating factors for underground cables laid in tier formation.

Current-carrying capacities may also be determined by calculation using IEC 60287 or applying correction factors to the published data from IEC 60364-5-52 for local conditions.

The subject of assigning a current-carrying capacity to a cyclically or intermittently loaded cable is not covered in this Standard as it normally relates to HV cable installation. However, reference may be made to ERA Report F/T 186 for information on the determination of such cable ratings by calculation.

1.4 REFERENCED AND RELATED DOCUMENTS

1.4.1 Referenced documents

The following documents are referred to in this Standard:

STANDARDS

AS/NZS 1125 Conductors in insulated electric cables and flexible cords

3000 Electrical installations (known as the Australian/New Zealand Wiring Rules)

3008 Electrical installations—Selection of cables 3008.1.2 Part 1.2: Cables for alternating voltages up to and including 0.6/1 kV—

Typical New Zealand installation conditions

IEC 60287 Electric cables—Calculation of the current rating (all Parts)

60364 Electrical installations of buildings 60364-4-43 Part 4-43: Protection for safety – Protection against overcurrent 60364-5-52 Part 5-52: Selection and erection of electrical equipment – Wiring systems

ERA REPORTS 69.30 Current rating standards for distribution cables

Part III: Sustained current ratings for PVC insulated cables to BS 6346:1969 (AC 50 Hz and DC)

69.30 Current rating standards for distribution cables

Part V: Sustained current ratings for cables with thermo-setting insulation to BS 5467:1989 and BS 6724:1986 (AC 50 Hz and DC)

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F/T 186 Methods for the calculation of cyclic rating factors and emergency loading for

cables laid direct in the ground or in ducts

1.4.2 Related documents

Attention is drawn to the following related documents.

AS 1531 Conductors—Bare overhead—Aluminium and aluminium alloy

1746 Conductors—Bare overhead—Hard-drawn copper

3158 Electric cables—Glass fibre insulated—For working voltages up to and including 0.6/1 (1.2) kV

AS/NZS 3191 Electric flexible cords

3560 Electric cables—Cross-linked polyethylene insulated—Aerial bundled—For up to and including 0.6/1 (1.2) kV

3560.1 Part 1: Aluminium conductors 3560.2 Past 2: Copper conductors

4026 Electric cables—For underground residential distribution systems

4961 Electric cables—Polymeric insulated—For distribution and service applications

5000 Electric cables—Polymeric insulated 5000.1 Part 1: For working voltages up to and including 0.6/1 (1.2) kV 5000.2 Part 2: For working voltages up to and including 450/750 V 5000.3 Part 3: Multicore control cables

60702 Mineral insulated cables and their terminations with a rated voltage notexceeding 750 V

60702.1 Part 1: Cables

IEC 60724 Short-circuit temperature limits of electric cables with rated voltages of 1.0 kV

(Um = 1,2 kV) and 3 kV (Um = 3,6 kV)

1.5 DEFINITIONS

For the purpose of this Standard, the definitions in AS/NZS 3000 and those below apply.

1.5.1 Ambient temperature

The temperature of the medium in the immediate neighbourhood of the installed cable—

(a) including any increase in temperature due to materials or equipment to which the cables are connected, or are to be connected; but

(b) excluding any increase in temperature that may be due to the heat arising from the cables at that point.

1.5.2 Continuous loading

A continuous constant current (100% load factor) just sufficient to produce asymptotically the maximum conductor temperature, the surrounding ambient conditions being assumed constant.

1.5.3 Installation wiring

A system of wiring in which the cables are fixed or supported in position in accordance with the appropriate requirements of this Standard. Replaces the term ‘fixed wiring’. A

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1.5.4 Ladder support

A support in which the impedance to the air flow around the cable is not greater than 10%, i.e. supporting metalwork under the cable occupies less than 10% of the plan area.

1.5.5 Perforated tray

A tray having not less than 30% of its surface area removed by the perforation.

1.5.6 Route length

The distance measured along a run of wiring from the origin of the circuit to the point of consideration, e.g. the distance measured between a switchboard and a motor.

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S E C T I O N 2 C A B L E S E L E C T I O N P R O C E D U R E

2.1 GENERAL

The cable selection procedures set out in this Section detail the guidelines to be followed to determine the minimum size of cable required to satisfy a particular installation condition.

2.2 SELECTION PROCESS

The following three main factors influence the selection of a particular cable to satisfy the circuit requirements:

(a) Current-carrying capacity Dependent upon the method of installation and the presence of external influences, such as thermal insulation, which restrict the operating temperature of the cable.

(b) Voltage drop Dependent upon the impedance of the cable, the magnitude of the load current and the load power factor.

(c) Short-circuit temperature limit Dependent upon energy produced during the short-circuit condition.

The minimum cable size will be the smallest cable that satisfies the three requirements. However, with experience it will become apparent that the different nature of installations will determine which of the requirements predominate. The current-carrying capacity requirement will be the most demanding in the relatively shorter route lengths of domestic premises and the like where factors such as cable grouping, and thermal insulation occur. On the other hand the voltage drop limitation is usually the deciding factor for longer route lengths that are not subject to the factors mentioned above. The need to increase cable size to meet the short-circuit temperature rise requirements will only occur in special situations for the voltage ratings of the cables covered by this Standard.

2.3 DETERMINATION OF MINIMUM CABLE SIZE BASED ON CURRENT-

CARRYING CAPACITY CONSIDERATIONS

To satisfy the current-carrying capacity requirements of a circuit it is necessary to take into account a number of factors, as follows:

NOTE: Refer to Appendix A for examples, in particular Example 3, which shows the method used

in this Clause.

(a) Determine the current requirements of the circuit. NOTE: Refer to the Clause in AS/NZS 3000 covering protection against overload current.

IB ≤ IZ

IB = the current for which the circuit is designed, e.g. maximum demand

IZ = the continuous current-carrying capacity of the cable determined by Clause 2.3(d).

(b) From Tables 3(1), 3(2), 3(3) and 3(4) determine the cable installation method to be used applicable to the common cross-linked elastomeric or thermoplastic-insulated cables. NOTE: Determine the current-carrying Table and appropriate column of the Table for use in

Clause 2.3(d).

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(i) For a single circuit, determine if the method of installation requires the application of a derating factor selected from Tables 22, 23 or 24. Where applicable, divide the value of current determined in Step (a) by the derating factor so determined.

(ii) For a group of circuits, determine if the method of installation requires the application of a derating factor selected from Tables 22 to 26. Where applicable, divide the value of current IB by the derating factor so determined.

(c) Determine the environmental conditions in the vicinity of the cable installation. Where applicable, divide the value of current determined in Step (b) by—

(i) the ambient air or soil temperature rating factor selected from Tables 27(1) and 27(2);

(ii) the depth of laying rating factor selected from Tables 28(1) and 28(2); and

(iii) the soil thermal resistivity rating factor selected from Table 29.

(d) The resulting value of current, determined from the calculations in Clauses 2.3(b) and 2.3(c), is used to select a cable from the current-carrying capacity Tables. This ensures that the cable will carry the design current IB as per Clause 2.3(a) after derating.

Refer to the Tables of current-carrying capacity for the different cable types, Tables 4 to 21. Taking into account the method of installation employed, the smallest conductor size that has a tabulated current-carrying capacity equal to or in excess of this pre-determined minimum value will be considered to be the minimum cable size satisfying the current-carrying capacity requirement.

IZ is the tabulated rating multiplied by the derating factors.

2.4 DETERMINATION OF MINIMUM CABLE SIZE BASED ON VOLTAGE DROP

CONSIDERATIONS

To satisfy the voltage drop limitations of a circuit, it is necessary to take into account the current required by the load and the route length of the circuit, as follows:

(a) Determine the current (I) requirements of the circuit.

(b) Determine the route length (L) of the circuit.

(c) Determine the maximum voltage drop (Vd) permitted on the circuit run. NOTE: Unless otherwise permitted by AS/NZS 3000, the maximum voltage drop between the

point of supply for the low voltage electrical installation and any point in that electrical

installation should not exceed 5% of the nominal voltage at the point of supply.

(d) Determine the voltage drop (Vc) in millivolts per ampere metre (mV/A.m) using Equation 4.2(1) and the values of I, L and Vd determined in Steps (a), (b) and (c).

(e) Refer to the tables of voltage drop (mV/A.m) for the different cable types, Tables 40 to 51. Taking into account the method of installation, maximum conductor operating temperature and load power factor, the smallest conductor size that has a tabulated voltage drop (mV/A.m) value nearest to, but not exceeding, the value determined in Step (d) will be considered to be the minimum cable size satisfying the voltage drop limitation.

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This simplified method gives an approximate but conservative solution assuming maximum cable operating temperatures and the most onerous relationship between load and cable power factors. A more accurate assessment can be made of the actual voltage drop (Vd) using the appropriate equation of Clause 4.5, the cable reactance determined from Tables 30 to 33, the cable a.c. resistance determined from Tables 34 to 39 using the approximate conductor operating temperature assessed from Equation 4.4(1), and the load power factor.

NOTES:

1 If the value of voltage drop assessed using the appropriate equation of Clause 4.5 is

significantly lower than the equivalent value determined using the simplified method

suggested in Steps (a) to (e), consideration should be given to the calculation of voltage drop

for the next smaller cable size.

2 Because of the need to make an initial set of assumptions relating to cable size, the

calculation method of Clause 4.5 will normally only be of use to check the accuracy of the

simplified method or to check the voltage drop on an existing or known cable installation.

2.5 DETERMINATION OF MINIMUM CABLE SIZE BASED ON THE

SHORT-CIRCUIT TEMPERATURE CONSIDERATIONS

To satisfy the short-circuit temperature limit it is necessary to take into account the energy producing the temperature rise (I2

t) and the initial and final temperatures, as follows:

(a) Determine the maximum duration and value of the prospective short-circuit current.

(b) Determine the initial and final conductor temperatures and select an appropriate value of the constant (K) from Table 52.

(c) Calculate the minimum cross-sectional area of the cable using Equation 5.3(1). This cable size represents the minimum size required to satisfy the short-circuit temperature rise requirements.

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S E C T I O N 3 C U R R E N T - C A R R Y I N G C A P A C I T Y

3.1 RATINGS

3.1.1 General

The provisions of this Section apply to the selection of conductor sizes with regard to current-carrying capacity.

Clauses 3.2 to 3.5 stipulate conductor and cable requirements and installation conditions in order that the subsequent tables of current-carrying capacity may be applied.

Tables 3(1) to 3(4) give guidance on the appropriate table of current-carrying capacity for different installation methods for the common types of cable insulation covered by Tables 4 to 15. A specific installation condition is defined and illustrated and alternative installation conditions deemed to have the same current-carrying capacity are also given. Attention is drawn to tables of rated current-carrying capacity where the standard installation conditions of Clause 3.4 are varied.

Tables 4 to 21 give the current-carrying capacities for the variety of different cable types described in Clause 3.3.

3.1.2 Basis

The values for current ratings given in Tables 4 to 15 have been calculated using the method described in IEC 60287 except for cables partially or completely surrounded by thermal insulation and flat cables that have been assigned the same ratings as circular cables.

NOTE: Unless otherwise stated, PVC wiring enclosures have been used for installation in air and

underground.

Furthermore it should be noted that the current ratings for 110°C rated cables enclosed in conduit

in air assume the use of metallic conduit. The use of non-metallic conduits are not recommended.

3.2 TYPES OF CONDUCTORS

3.2.1 Conductor material

The current-carrying capacities are based on conductors of high-conductivity copper and aluminium in sizes, strandings and resistances complying with AS/NZS 1125.

3.2.2 Insulation material operating temperatures

The sustained current-carrying capacities are based on the ‘normal use’ temperatures specified in Column 2 of Table 1. Where the ‘maximum permissible’ temperature in Column 3 of Table 1 is greater than the ‘normal use’ temperature, the ‘maximum permissible’ temperature may only be used under the conditions described in Note 3 to Table 1 for thermoplastic cables and in Note 7 to Table 1 for MIMS cables.

NOTE: Where cables are consistently operating substantially below the limiting temperature of

Table 1, the heat losses (I2R) and voltage drop (IZ) will also be reduced. These features could be

relevant in determining the optimum economic design of a circuit.

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TABLE 1

LIMITING TEMPERATURES FOR INSULATED CABLES

1 2 3 4

Type of cable insulation Operating temperatures of conductors, °C

(see Note 1)

Normal use Maximum

permissible

(see Note 2)

Minimum

ambient

Thermoplastic (see Note 3)

V-75

HFI-75-TP, TPE-75

V-90

HFI-90-TP, TP-90

V-90HT

75

75

75

75

75

75

75

90

90

105

0

-20

0

-20

0

Cross-linked elastomeric (see Note 4)

R-EP-90

R-CPE-90, R-HF-90, R-CSP-90

R-HF-110, R-E-110 (see Note 5)

R-S-150 (see Note 6)

90

90

110

150

90

90

110

150

-40

-20

*

-50

Cross-linked polyolefin (XLPE) (see Note 4)

X-90, X-90UV, X-HF-90

X-HF-110 (see Note 5)

90

110

90

110

*

*

Mineral-insulated metal-sheathed (MIMS)

(see Note 7)

100 (sheath)

250 (sheath)

–

Other types

PE, LLDPE

Type 150 fibrous or polymeric (see Note 6)

70

150

70

150

*

–

* Refer to manufacturer’s information

NOTES:

1 The temperature limits specified in Table 1 relate to the sustained current-carrying capacity and do not

represent the maximum permissible temperatures permitted under short-circuit conditions. A guide to the

acceptable short-circuit temperature limits is given in Section 5.

2 The maximum permissible temperatures given in Column 3 are applicable when there is no chance of

thermal deformation or a reasonable chance of human contact in normal use.

For safety reasons, where flexible cords may be exposed and are likely to be touched, the maximum

permissible temperature should be limited (see Note 3 to Table 16).

3 The normal operating temperature of thermoplastic cables, including flexible cords installed as installation

wiring, are based on a conductor temperature of 75°C. This is due to the risk of thermal deformation of

insulation if the cables are clipped, fixed or otherwise installed in a manner that exposes the cable to

severe mechanical pressure at higher temperatures.

V-90 and V-90HT insulated cables may be operated up to the maximum permissible temperatures 90°C

and 105°C provided that the cable is installed in a manner that is not subject to, or is protected against,

severe mechanical pressure at temperatures higher than 75°C. Such applications also allow for cables to be

used in—

(a) locations where the ambient temperatures exceeds the normal 40°C, e.g. equipment wiring in

luminaires and heating appliances, or in roof spaces affected by high summer temperatures; and

(b) locations affected by bulk thermal insulation that restricts the dissipation of heat from the cable.

4 Cross-linked elastometric and cross-linked polyolefin materials have the property of maintaining their

shape at higher temperatures and do not flow under mechanical pressure.

5 Cables with an operating temperature of 110°C should only be connected to equipment suitable for this

temperature. Consideration should also be given to the voltage drop at this operating temperature.

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6 The current-carrying capacities given in Table 17 for cables insulated with high temperature cross-linked

elastomeric, polymeric or fibrous materials are based on cables operating at temperatures of 150°C in an

ambient temperature of 40°C and where the hot cable surfaces are acceptable. However, the cables are

generally installed in areas of high ambient temperature, such as equipment wiring, and it will be

necessary to apply an appropriate temperature correction factor from Table 27.

The current-carrying capacities for fibrous and polymeric (fluoropolymer) type cables and cords suitable

for operation at 200°C are not given in this Standard. As an alternative to the use of the relatively

conservative values given in Table 27, advice may be sought from cable manufacturers.

7 The current-carrying capacities for MIMS cables are based on an operating temperature of 100°C for the

external surface of either bare metal-sheathed cables or served cables. Higher continuous operating

temperatures are permissible for bare metal-sheathed cables, particularly stainless steel sheathed cables,

dependent upon factors such as the following:

(a) The suitability of the cable terminations and mountings.

(b) The location of the cable away from combustible materials.

(c) The location of the cable away from areas where there is a reasonable chance of persons touching

the exposed surface.

(d) Other environmental and external influences.

3.3 TYPES OF CABLE

3.3.1 Sheathed or unsheathed thermoplastic, cross-linked elastomeric and XLPE

insulated cables

3.3.1.1 General

The current-carrying capacity of sheathed or unsheathed thermoplastic, cross-linked elastomeric or XLPE insulated cables shall be determined from Tables 4 to 15.

3.3.1.2 Method of installation

The current-carrying capacity of a given cable depends on the method of installation. Tables 3(1) to 3(4) provide a schedule of the installation methods applicable to sheathed or unsheathed cross-linked elastomeric or thermoplastic insulated cables whose current-carrying capacities are given in Tables 4 to 15. Tables 3(1) to 3(4) also draw attention to the different methods of installation that may be assigned the same current-carrying capacity and refers to tables of derating factors applicable where one circuit is run in close proximity to another circuit or circuits.

3.3.2 Flexible cords and cables

3.3.2.1 Used for installation wiring

The determination of current-carrying capacity of flexible cords and cables used for installation wiring shall be as given in Tables 4 to 15 and 17.

3.3.2.2 Other than installation wiring

The determination of current-carrying capacity of flexible cords and cables used for other than installation wiring shall be as follows:

(a) General Except as provided in Item (b), the current-carrying capacity of flexible cords and cables not used as installation wiring shall be determined from Tables 16 and 17. The current-carrying capacity of flexible cables shall be determined from Tables 4 to 15.

(b) Connection of equipment Where a flexible cord is—

(i) used for the connection of equipment to the installation wiring by means of a plug and socket; and

(ii) the equipment comes within the scope of associated Standards;

the current-carrying capacity shall be determined from the appropriate Standard.

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3.3.3 Mineral-insulated metal-sheathed (MIMS) cables

The current-carrying capacity of bare or served copper MIMS cables shall be determined from Tables 18 and 19.

NOTE: Current–carrying capacities are not given in this Standard for polyethylene served or

other forms of MIMS cable used for heating purposes, such as trace heating, tank heating or floor

warming.

3.3.4 Aerial cables

The current-carrying capacity of aerial cables shall be determined from Tables 20 and 21. See Clause 3.3.5 for the determination of the current-carrying capacity of neutral-screened aerial cables.

3.3.5 Neutral-screened cables

The current-carrying capacity of neutral-screened cables shall be determined from the number of cable cores and method of installation as follows:

(a) For single-core neutral-screened cables (i.e. 2-conductors).

Tables 10, 11 and 12.

(b) For 2-core, 3-core or 4-core neutral-screened cables (i.e. 3-conductor, 4-conductor and 5-conductor).

Tables 13, 14 and 15.

However, the current-carrying capacity of neutral-screened aerial cables shall be determined as follows:

(i) For 2-core (i.e. 3-conductor) neutral-screened cable.

Columns 8 to 10 and 15 to 17 of Table 20 or Table 21, as appropriate.

(ii) For 2-core, 3-core or 4-core (i.e. 3-, 4- or 5-conductor) neutral screened cable.

Columns 12 to 14 and 18 to 20 of Table 20 or Table 21, as appropriate.

3.3.6 High temperature cross-linked elastomeric, polymeric or fibrous insulated

cables and flexible cords

The current-carrying capacity of R-S-150 cross-linked elastomeric insulated cables, Type 150 heat-resisting fibrous insulated cables and 150°C rated fluoropolymer insulated flexible cords shall be determined from Table 17.

3.3.7 Other cable types

This Standard provides current-carrying capacities for types of cables that are considered to be in common use. For cables not included in this Standard, cable manufacturers should be consulted for recommendations on the current-carrying capacity and acceptable methods of installation.

3.4 INSTALLATION CONDITIONS

3.4.1 General

The current-carrying capacity of a cable is dependent on the method of installation to maintain the temperature of the cable within its operating limits. Different methods of installation vary the rate at which the heat generated by the current flow is dissipated to the surrounding medium.

Specific conditions of installation are laid down in Clauses 3.4.2 to 3.4.5 for cables installed with or without wiring enclosures in air, in the ground or embedded in building materials. These conditions have been used to derive the current-carrying capacities tabulated in Section 3. Where a number of installation conditions exist along a cable run or variations to the specific conditions occur, reference shall be made to Clauses 3.4.6 and 3.5 respectively.

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3.4.2 Cables installed in air

For cables installed in free air, the current-carrying capacities shall be based on the following conditions of installation and operation:

(a) Ambient temperature An ambient air temperature of 40°C.

(b) Unenclosed cables Cables installed as follows:

(i) Directly in air and, except for flexible cables as mentioned in Note 2 to Table 1 and aerial cables, not exposed to direct sunlight and where they are—

(A) lying on a horizontal surface;

(B) lying across ceiling joists;

(C) supported on perforated or unperforated cable trays, ladders, hangers or racks;

(D) clipped at intervals to a vertical or horizontal surface, such as a wall or beneath a ceiling;

(E) suspended from a catenary wire;

(F) lying in the bottom of open trunking; or

(G) in an enclosure such as a switchboard.

(ii) Directly embedded beneath the surface of plaster, cement render or masonry. NOTE: Table 3(1) contains a reference to the appropriate current-carrying capacity table for

cables installed unenclosed in air.

(c) Enclosed cables Cables installed as follows:

(i) In metallic or non-metallic wiring enclosure in—

(A) free air;

(B) a ventilated or enclosed trench;

(C) a concrete slab on or above the surface of the ground; or

(D) a concrete, plaster, cement rendered or masonry wall.

(ii) In closed trunking.

(iii) In an enclosed trench with removable covers.

(iv) Directly buried in concrete. NOTES:

1 Table 3(2) contains a reference to the appropriate current-carrying capacity table for

enclosed cables installed in air.

2 Where an otherwise unenclosed cable run includes short lengths of wiring enclosure that

do not restrict the free circulation of air, the current-carrying capacity for unenclosed

conditions may be assigned to the cable run provided that the following are complied

with:

(a) The total above-ground sections do not exceed half the length of the cable run or 6 m, whichever is the shorter dimension.

(b) The wiring enclosure is not surrounded by thermal insulation.

(c) The wiring enclosure is of adequate size to permit free air circulation to dissipate any heat arising from the enclosed cables. This would be satisfied if the wiring enclosure—

(i) has a bore area not less than twice the total cross-sectional area of the enclosed

live cables;

(ii) is arranged in a substantially vertical direction; and

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(iii) has an open upper end or other means that will not restrict the escape of hot air

to the surroundings. 3 Selection of wiring enclosure material needs to take into account the highest sheath

temperature of the cable.

3.4.3 Cables installed in thermal insulation

For cables installed in thermal insulation the current-carrying capacities shall be based on the following conditions of installation and operation:

(a) Ambient temperature An ambient temperature of the air surrounding the thermal insulation of 40°C.

(b) Unenclosed cables Cables installed without further enclosure—

(i) lying on a horizontal surface;

(ii) lying across ceiling joists;

(iii) supported on perforated or unperforated cable trays, ladders, hangers or racks;

(iv) clipped at intervals to a vertical or horizontal surface such as a wall or ceiling joist; or

(v) lying in the bottom of open trunking.

(c) Enclosed cables Cables installed in—

(i) metallic or non-metallic wiring enclosure; or

(ii) closed trunking or ducts.

(d) Bulk thermal insulation Bulk thermal insulation installed as follows:

(i) Materials Building materials installed to provide a thermal insulation including—

(A) fibreglass or rockwool batts;

(B) cellulose fibre, paper, cork, seagrass or similar organic materials that are normally installed in a loose-fill form; or

(C) expanded synthetic foams such as polystyrene, ureaformaldehyde or polyurethane, which may be installed by pumping or injection as a wet foam.

NOTE: Reflective foil laminates are not considered to be bulk thermal insulation.

(ii) Completely surrounded installation An installation method where bulk thermal insulation surrounds, and is in contact with, unenclosed or enclosed cables.

(iii) Partially surrounded installation An installation method where bulk thermal insulation is prevented from completely surrounding unenclosed or enclosed cable, such as where an unenclosed or enclosed cable is clipped to a structural member or is lying on a ceiling.

NOTE: Table 3(2) contains a reference to the appropriate current-carrying capacity table for

cables installed in thermal insulation.

3.4.4 Cables buried direct in the ground

For cables buried direct in the ground, the current-carrying capacities shall be based on the following conditions of installation and operation:

(a) Ambient temperature An ambient soil temperature of 25°C.

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(b) Depth of laying A depth of laying of 0.5 m measured from the ground surface to the centre of a cable, or to the centre of a trefoil group of cables.

(c) Thermal resistivity of soil A soil thermal resistivity of 1.2°C.m/W.

(d) Spacing of cables Cables are spaced as follows:

(i) Single-core cables Either—

(A) three single-core cables laid touching throughout in trefoil formation; or

(B) two or three single-core cables laid touching in flat formation.

(ii) Multicore cables Multicore cables laid singly. NOTE: Table 3(3) contains a reference to the appropriate current-carrying capacity table for

cables buried direct in the ground. See Clause 3.5.2.5 for spacing distances.

3.4.5 Cables installed in underground wiring enclosures

For cables installed in underground wiring enclosures, the current-carrying capacities shall be based on the following conditions of installation and operation:

(a) Ambient temperature An ambient soil temperature of 25°C.

(b) Depth of laying A depth of laying of 0.5 m measured from the ground surface to the centre of a wiring enclosure, or to the centre of a trefoil group of wiring enclosures.

(c) Thermal resistivity of soil A soil thermal resistivity of 1.2°C.m/W.

(d) Spacing of wiring enclosures Wiring enclosures shall be spaced as follows:

(i) Single-core cables in separate wiring enclosures with—

(A) two ducts side by side touching; or

(B) three ducts in trefoil, or in flat formation touching.

(ii) Single-core cables as a circuit in a single wiring enclosure.

(iii) Multicore cable in a single wiring enclosure. NOTE: Table 3(4) contains a reference to the appropriate current-carrying capacity table for

cables installed in underground wiring enclosures. See Clause 3.5.2.6 for spacing distances.

3.4.6 Variation of installation conditions along cable run

In situations where one method of installation is used for part of a cable run and other methods for the remainder, the current-carrying capacity of the cable run shall be limited to the lowest value of current determined for each method of installation employed, unless precautions to avoid cable overheating are taken.

NOTES:

1 An example of appropriate precautions is where long runs of cable buried direct in the ground

are enclosed in wiring enclosures when passing beneath roadways and the like. The use of

selected backfill materials over the enclosed cables can improve the conduction of heat away

from the cables and as a consequence higher current-carrying capacities, in the order of that

for buried direct cables, can be sustained by the short lengths of enclosed cables.

2 Note 2 to Clause 3.4.2 (c) describes a situation where a short length of suitably arranged

enclosure may be disregarded for the assignment of a current-carrying capacity to an

otherwise unenclosed cable run in air.

3 Attention is drawn to the connection of equipment to an underground cable run by means of

short lengths of enclosed or unenclosed cables in air. The current-carrying capacity assigned

to the underground portion of the cable run may be assigned to the above-ground portion

where the prevailing installation conditions maintain the final operating temperature of the

cable within the limits given in Table 1.

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3.5 EXTERNAL INFLUENCES ON CABLES

3.5.1 Application of rating factors

The current-carrying capacity of a cable will be affected by the presence of certain external influences as detailed in Clauses 3.5.2 to 3.5.8. Under such conditions the current-carrying capacity given in Tables 4 to 21 shall be corrected by the application of an appropriate rating factor or factors obtained from Tables 22 to 29.

3.5.2 Effect of grouping of cables

3.5.2.1 General

The current-carrying capacities given in Tables 4 to 21 relate to single circuits.

Where a number of circuits are installed in the same group in free air, on a surface, buried direct in the ground or within the same sheath or wiring enclosure, in such a way that they are not independently cooled by the ambient air or the ground, the appropriate derating factor shall be as given in Tables 26 to 30.

Specific guidance on the use of Tables 22 to 26 is given in Clauses 3.5.2.3 to 3.5.2.7 and Table 3.

NOTES:

1 The derating factors have been calculated on the basis of sustained operation of all cables

within the group. In most instances the loading on all cables in the group will not occur

simultaneously and as a result actual factors may vary from those in Tables 22 to 26. Actual

values would need to be calculated according to loading.

2 Where cables of different temperature rating are grouped, they should be rated at the rating

appropriate to the lowest temperature cable, unless adequate spacing is provided in

accordance with Figure 1.

3.5.2.2 Installation conditions that avoid derating

The derating factors of Tables 22 to 26 are not applicable to the following conditions of grouped cables:

(a) MIMS cables MIMS cables without serving unless other types of cables are installed in close proximity or within the same wiring enclosure. The higher operating temperature achieved by grouping will not affect the mineral insulation of the unserved cable. However, care must be taken that the cable environment and means of support can withstand the higher temperatures. NOTE: See Note 5 to Table 1.

(b) Limited length of grouping Groups of cables such as at a switchboard entry, provided that the length of wiring enclosure does not exceed—

(i) for conductor sizes smaller than 300 mm2 for aluminium or smaller than 150 mm2 for copper: 1 m;

(ii) for conductor sizes of 300 mm2 or larger for aluminium and 150 mm2 or larger for copper: 3 m; or

(iii) half the length of the cable;

whichever is the shorter dimension.

(c) Groups of circuits in free air Groups of circuits installed unenclosed under the conditions and circuit arrangements depicted in Figure 1.

(d) Cables operating below current-carrying capacity Cables that, as a result of the conditions of operation of the installation or cable selection practices, are operating at less than 35% of their current-carrying capacity (see Figure 1, Note 3).

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Method of installation Horizontal spacings Vertical spacings

Cables suspended from a catenary

wire where air circulation is

unrestricted or spaced from surfaces

and supported on ladders, racks,

hangers or cleats where the

impedance of the air flow around the

cable is not greater than 10%

Cables spaced from surfaces and

supported on perforated or

unperforated cable trays where air

circulation is partially restricted

Cables fixed directly to a wall, floor,

ceiling or similar surface where air

circulation is restricted

(a) Single-core cables

Method of installation Horizontal spacings Vertical spacings

Cables suspended from a catenary

wire where air circulation is

unrestricted or spaced from surfaces

and supported on ladders, racks,

hangers or cleats where the

impedance of the air flow around the

cable is not greater than 10%

Cables spaced from surfaces and

supported on perforated or

unperforated cable trays where air

circulation is partially restricted

Cables fixed directly to a wall, floor,

ceiling or similar surface where air

circulation is restricted

(b) Multicore cables

FIGURE 1 MINIMUM CABLE SPACINGS IN AIR TO AVOID DERATING

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NOTES TO FIGURE 1:

1 D equals the cable outside diameter or in the case of a flat multicore cable the maximum dimension of the

cable.

2 For simplicity, the illustrations depict balanced multiphase circuits. Where a neutral conductor is required

to be substantially loaded, it shall be placed adjacent to the associated active conductors and the clearance

measured as appropriate (see Note 3 for lightly loaded or unloaded conductors).

3 The illustrations are intended to depict clearances required between cables operating at or near their

sustained current-carrying capacity. Where the loading of any cable is less than 35% of such sustained

capacity it may be disregarded from the cable arrangements as its contribution to the mutual heating of the

group will be small. Such cables, which would include earthing conductors, lightly loaded neutrals and

unloaded control wiring, may be placed adjacent to, or between, groups of associated loaded conductors.

4 Where the cables concerned are not of the same size, the spacing will be based on the largest cable

diameter in the adjacent groups.

5 The spacings are essentially minimum requirements to avoid derating and care should be taken, particularly

with smaller spacings, to avoid installation methods that would reduce these clearances. No restriction is

placed on the number of circuits that may be arranged horizontally with the spacings given. However, care

should be taken if more than three circuits are arranged vertically and full cable utilization is required.

6 Where the spacings are not achieved, smaller spacings and derating factors are laid down in the following

tables:

(a) For circuits installed directly on walls, floors or ceilings ...................................................................... Table 22.

(b) For circuits installed on trays, ladder supports, racks, hangers or cleats...................................Tables 23 and 24.

7 Proportionally smaller spacings would be acceptable where the cables in the group are not loaded to the

full current-carrying capacity. In such cases appropriate rating factors may be obtained from ERA Report

69-30.

3.5.2.3 Cables run horizontally

For cables installed horizontally the following shall apply:

(a) Unenclosed on cable tray, ladder support, rack hanger or cleat Where a single-core or multicore cable is installed horizontally in close proximity to a cable or cables of another circuit and—

(i) it is on perforated or unperforated trays, ladder supports, racks, hangers or cleats; and

(ii) it is either—

(A) touching the other cable or cables; or

(B) in terms of its spacing from the other cable or cables, less than that specified in Clause 3.5.2.2(c) and Figure 1;

the appropriate derating factor shall be as given in Table 23 or Table 24.

(b) Enclosed, fixed to a surface, or bunched in free air Where a single-core or multicore cable is installed horizontally in close proximity to a cable or cables of another circuit—

(i) within a wiring enclosure;

(ii) on a surface, wall, floor or ceiling, spaced or touching;

(iii) bunched in free air; or

(iv) suspended from a catenary;

the appropriate derating factor shall be as given in Table 22.

3.5.2.4 Cables run vertically

Where a cable is installed vertically, the appropriate current-carrying capacities and derating factors shall be—

(a) obtained from Tables 22 to 24 as for cables run horizontally; and Acc

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(b) determined in accordance with Clause 3.5.3 using the highest ambient air temperature up the cable run, if a barrier is not provided at intervals of 3.5 m or less to prevent the vertical flow of air along the cable.

3.5.2.5 Cables buried direct in the ground

Where a single-core or multicore cable is buried directly in the ground and is separated by not less than 2 m from a cable or cables of another circuit carrying substantial currents, no derating factor need be applied. Where the circuits are separated by less than 2 m, the appropriate derating factor shall be obtained from Table 25 or, for installation methods not covered in this Standard, alternative specifications as recommended in Clause 1.3.

NOTE: The derating factors have been determined from the hottest cable in the group and assume

that all cables are of the same thermal grade of insulation.

3.5.2.6 Cables in wiring enclosures

For cables in enclosures the following shall apply:

(a) Underground wiring enclosures Where a single-core or multicore cable is installed in an underground wiring enclosure and is separated by not less than 2 m from a cable or cables of another enclosed circuit carrying substantial currents, no derating factor need be applied. Where the enclosed circuits are separated by less than 2 m, the appropriate derating factor shall be as given in Table 26 or, for installation methods not covered in this Standard, alternative specifications as recommended in Clause 1.3.

(b) Other enclosures Where cables are installed in an enclosure such as a switchboard, the current-carrying capacity shall be determined from the unenclosed in air conditions in Tables 4 to 10 with due regard being given to the derating factors when circuits are bunched.

NOTE: The selection of the derating factor should be based on the number of circuits that would

be loaded; for example, where nine circuits are bunched but only six are loaded at any one time, a

derating factor of 0.57 from Table 22 would be applicable.

3.5.2.7 Conductors connected in parallel or passing more than once within a group or

enclosure

In applying the derating factors of Tables 22 to 26 where—

(a) a group of conductors forming a circuit passes more than once through the same wiring enclosure, group of cables or group of enclosures; or

(b) groups of conductors are connected in parallel;

each separate group of conductors shall be regarded as a separate circuit.

3.5.2.8 Cables on drums or reels

Where layers of flexible cables are wound on a cylindrical-type drum or reel, the current-carrying capacity of the cable shall be derated by the appropriate factor, as follows:

Number of layers: 1 2 3 4

Derating factor: 0.85 0.65 0.45 0.35

Where a single spiral layer of flexible cable is accommodated on a radial-type drum, the current-carrying capacity of the cable shall be derated by a factor of 0.85 for ventilated drums and 0.75 for unventilated drums.

3.5.3 Effect of ambient temperature

The current-carrying capacities given in the tables of this Standard are based on a consistent ambient air temperature of 40°C and an ambient soil temperature of 25°C. Where other ambient temperatures apply, the appropriate rating factors shall be as given in Table 27.

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NOTES:

1 In New Zealand the conditions of installation specify an ambient temperature of 30°C and a

soil temperature of 15°C. A complete set of current rating tables, calculated for New Zealand

conditions, is given in AS/NZS 3008.1.2.

2 Particular consideration should be given to the existence of higher ambient air temperatures in

confined roof spaces, boiler rooms, cable tunnels, vertical shafts and the like. Similarly, lower

ambient temperatures may apply for cables installed in concrete slabs on or above the surface

of the ground.

3 In practice the ambient air temperature may be measured by one of the following simple

methods:

(a) Before installation of cables Measurement may be made by temperature sensors

placed in free air as close as practicable to the position at which the cables are to be

installed.

(b) After installation of cables Measurement may be made by temperature sensors placed

in free air in the vicinity of the cables in such a position that readings are not

influenced by heat arising from the cables. Where the measurements are made while

the cables are loaded, e.g. as may be required by Clause 3.5.2.4 for vertical cable runs,

the sensors should be placed approximately 500 mm, or 10 times the overall diameter

of the cable, from the cables in a horizontal plane, or 150 mm below the cables.

If at the cable position, the ambient temperature, including any increase of temperature due to heat arising from equipment to which the cables are connected, does not exceed 40°C except for infrequent combinations of weather and load currents, then the current-carrying capacities given in the tables apply without correction.

3.5.4 Effect of depth of laying

The current-carrying capacities given in the tables of this Standard are based on a depth of laying of 0.5 m as specified in Clauses 3.4.4 and 3.4.5. Where other depths of laying apply, the appropriate rating factors shall be as given in Table 28.

NOTE: The rating factors are based on the assumption that the effective thermal resistivity of the

ground is constant from a depth of 0.5 m to 3 m. Above and below these respective limits it is

considered that a reduction in effective thermal resistivity occurs due to the composition and

moisture content of the soil.

3.5.5 Effect of thermal resistivity of soil

The current-carrying capacities given in the tables of this Standard are based on a soil thermal resistivity of 1.2°C.m/W.

Soil thermal resistivity varies greatly with soil composition, moisture retention qualities and seasonal weather patterns as well as the variation in load carried by the cable. Higher current-carrying capacities are obtained in clay or peat soils, which may have resistivities as low as 0.8°C.m/W. Similarly, values as high as 2.5°C.m/W may be associated with well drained sands for constantly loaded cables. The value of 1.2°C.m/W has been selected as an average figure on the basis of soil types and assumes maximum thermal resistivity at times of maximum load.

If possible the actual value should be measured along the cable route as it can greatly affect the current-carrying capacity of the cable. Where values for soil resistivities other than 1.2°C.m/W apply, the appropriate rating factors may be obtained from Table 29.

NOTE: Where the soil is known to be of poor quality and has a thermal resistivity greater than

1.2°C.m/W throughout much of the year, consideration should be given to the use of a selected or

stabilized backfill material around the cables or wiring enclosures.

Such backfill should completely surround the cable with a minimum thickness of 200 mm and

could be used in lieu of the bedding required in AS/NZS 3000.

The following two types of material have a worst-case or dried-out thermal resistivity in the order

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(a) Cement-bound sand A mixture of sand bound with cement in the ratio of 14:1 by volume,

with water added to enable adequate compaction to be achieved.

(b) Gravel/sand A mixture of a selected sand having a dried-out thermal resistivity of not

greater than 2.7°C.m/W, with an equal quantity of 10 mm coarse aggregate.

3.5.6 Effect of varying loads

The current-carrying capacities given in the tables of this Standard and the derating factors given in Clauses 3.5.2 to 3.5.5 are based on continuous loading on all conductors. Where it can be shown that intermittent load variations will occur or that all conductors cannot be loaded simultaneously, appropriate uprating factors may be applied.

In many installations, groups of cables comprise a mixture of loaded and unloaded cables at any one time and the designer may justify the use of alternative derating factors to those specified in Tables 22 to 26, if the connected loads have a known diversity. If the diversity is unknown or unobtainable by experiment, the design may have to be based on worst-case analysis of the possible load combinations at any one time. Some information on the diversity of certain loads may be obtained from the determination of maximum demand in AS/NZS 3000.

3.5.7 Effect of thermal insulation

Current-carrying capacities are given in Tables 4 to 15 of this Standard for unenclosed or enclosed cables surrounded by bulk thermal insulating materials that affect the rate of heat dissipation from the cables.

The rate of heat dissipation varies with the type and thickness of material used. A comparative measure of the performance of different materials is known as the R-factor.

The current-carrying capacity values in the tables are based upon typical installation conditions and a range of different materials as described in Clause 3.4.3. Where different materials or installation conditions are used such that the rate of heat dissipation is adversely or favourably affected, lower or higher current-carrying capacities may be obtained respectively.

NOTES:

1 Where a length of cable not exceeding 150 mm passes through bulk thermal insulation,

e.g. for the connection of a lighting point, the cable need not be considered as being

surrounded by thermal insulation.

2 A cable is considered to be affected by thermal insulation if it is embedded in, or surrounded

by, insulating material. Cables lying on top of suitably rigid material do not in general come

into this consideration.

3.5.8 Effect of direct sunlight

Current-carrying capacities are given in Tables 4 to 15, 20 and 21 for cables exposed to direct sunlight. For other types of cable installed in locations exposed to direct solar radiation it will be necessary to make some provision for the effects of the increased heating. This may be achieved by one of the following means:

(a) Provision of a shield, screen or enclosure that allows for the natural ventilation of the cable.

(b) Reduction of the current-carrying capacity of the cable by an appropriate amount in accordance with the higher air temperature. As a rule-of-thumb alternative to any recommendation from a cable manufacturer, a correction factor obtained from Table 27(1) for a temperature 20° higher than the ambient air temperature may be applied.

NOTE: For further information on the effects of ultraviolet radiation, it is recommended that the

cable manufacturer be consulted.

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3.5.9 Effect of harmonic currents on balanced three-phase systems

Where the neutral conductor carries current without a corresponding reduction in load of the phase conductors, the current flowing in the neutral conductor shall be taken into account in ascertaining the current-carrying capacity of the circuit.

This clause is intended to cover the situation where there is current flowing in the neutral of a balanced three-phase system. Such neutral currents are due to the line currents having a harmonic content that does not cancel in the neutral. The most significant harmonic that does not cancel in the neutral is usually the third harmonic. The magnitude of the neutral current due to the third harmonic may exceed the magnitude of the power frequency phase current. The neutral current will then have a significant effect on the current-carrying capacity of the cables in the circuit.

The reduction factors given in this Clause apply to balanced three-phase circuits; it is recognized that the situation is more onerous if only two of the three phases are loaded. In this situation the neutral conductor will carry the harmonic currents in addition to the unbalanced current. Such a situation can lead to overloading of the neutral conductor.

Equipment likely to cause significant harmonic currents are, for example, fluorescent lighting banks and d.c. power supplies such as those found in computers.

The reduction factors given in Table 2 only apply to cables where the neutral conductor is within a four- or five-core cable and is of the same material and cross-sectional area as the phase conductors. These reduction factors have been calculated based on third harmonic currents. If significant, more than 10%, higher harmonics, 9th, 12th, etc. are expected then lower reduction factors are applicable. Where there is an unbalance between phases of more than 50% then lower reduction factors may be applicable.

The tabulated reduction factors, when applied to the current-carrying capacity of a cable with three loaded conductors, will give the current-carrying capacity of a cable with four loaded conductors where the current in the fourth conductor is due to harmonics. The reduction factors also take the heating effect of the harmonic current in the phase conductors into account.

Where the neutral current is expected to be higher than the phase current then the cable size should be selected on the basis of the neutral current.

Where the cable size selection is based on a neutral current that is not significantly higher than the phase current, it is necessary to reduce the tabulated current-carrying capacity for three loaded conductors.

If the neutral current is more than 135% of the phase current and the cable size is selected on the basis of the neutral current then the three-phase conductors will not be fully loaded. The reduction in heat generated by the phase conductors offsets the heat generated by the neutral conductor to the extent that it is not necessary to apply any reduction factor to the current-carrying capacity for three loaded conductors.

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TABLE 2

REDUCTION FACTORS FOR HARMONIC CURRENTS

IN 4- AND 5-CORE CABLES

Third harmonic

content of phase

current

%

Reduction factor

Size selection is based

on phase current

Size selection is based

on neutral current

0 – 15 1.0 —

15 – 33 0.86 —

33 – 45 — 0.86

> 45 — 1.0

NOTE: Examples of the application of reduction factors for harmonic currents are provided in

Appendix C.

3.5.10 Effect of parallel cables

Current-carrying capacities for circuits comprising parallel multicore cables or groups of single-core cables can be determined from the sum of the current-carrying capacity of the various cables provided that consideration is given to—

(a) grouping cables and the effect of cooling by the ambient air or the ground on each parallel cable or group; and

(b) load current sharing between each parallel cable or group so as to prevent overheating of any cable or group.

Equal load current sharing is generally achieved by the selection and installation of cables to give the same impedance, i.e. by using cables of the same conductor material and construction installed over the same route. Mutual impedance is also affected by the configuration of cables within and between each group.

NOTES:

1 Table D1 of Appendix D provides recommended circuit configurations for the installation of

parallel single-core cables in electrically symmetric groups. The recommended method is to

use trefoil groups containing each of the three-phase conductors and neutral in each group.

2 Unequal load current sharing between cables or groups may be permitted provided that the

design current and overcurrent protection requirements for each cable or group are considered

individually. IEC 60364-4-43 provides further information on the conditions under which this

is permitted.

3.5.11 Effect of electromagnetic interference

Certain types of electrical installations, e.g. those containing sensitive electronic equipment or systems, may require minimization of electromagnetic interference arising from magnetic fields developed from current flowing in cables. This may be addressed by—

(a) selection of cables designed for low magnetic field emissions; or

(b) installation of cables in enclosures that contain or shield magnetic fields; or

(c) installation of cables in configurations that produce low magnetic fields. NOTE: Table D1 of Appendix D provides recommended circuit configurations for the installation

of parallel single-core cables in groups that produce reduced levels of magnetic field.

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TABLE 3(1)

SCHEDULE OF INSTALLATION METHODS FOR CABLES DEEMED TO HAVE

THE SAME CURRENT-CARRYING CAPACITY AND CROSS-REFERENCES TO

APPLICABLE DERATING TABLES—UNENCLOSED IN AIR

1 2 3 4 5 6

Item

No.

Cable details

(see Note 2)

Reference drawing

(see Note 3)

Current-carrying

capacity table

reference

Methods of installation for cables

deemed to have the same current-

carrying capacity

(See Notes 4, 5 and 6)

Derating table

1 Two single-

core cables

Tables 4 and 5

Columns 2 to 4

Table 6

Columns 2 and 3

Cables with minimum cable

separation in air as shown for

horizontal and vertical mounting and

installed—

(a) spaced from a wall or vertical

surface;

(b) supported on ladders, racks,

perforated trays, cleats or

hanger;

or

23

2 Three single-

core cables

Tables 7 and 8

Columns 2 to 4

Table 9

Columns 2 and 3

3 (c) suspended from a catenary wire. 22

4 Two single-

core cables

Tables 4 and 5

(see Note 5)

Columns 5 to 7

Table 6

Columns 2 and 3

Cables with minimum cable

spacings in air as shown and

installed—


surface;


perforated or unperforated

trays, cleats or hangers;

(c) in a switchboard or similar

enclosure;

or

23

5 Three single-

core cables

Tables 7 and 8

(see Note 5)

Columns 5 to 7

Table 9

Columns 4 and 5 6 (d) suspended from a catenary wire. 22

7 Two single-

core cables

Tables 4 and 5

(see Note 4)

Columns 8 to 10

Table 6

Columns 6 and 7

Cables of the one circuit touching

and installed—

(a) clipped direct to a wall, floor,

ceiling or similar surface;

(b) in a ventilated trench or open

trunking;

(c) buried directly in a plaster or

render on a wall; or

(d) in a switchboard or similar

enclosure.

22

8 Three single-

core cables

Tables 7 and 8

(see Note 4)

Columns 8 to 10

Table 9

Columns 6 and 7.

(continued)

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1 2 3 4 5 6

Item

No. Cable details

(see Note 2)

Reference drawing

(see Note 3)

Current-carrying

capacity table

reference



carrying capacity

(See Notes 4, 5 and 6)

Derating table

9 Two-core

cables

Tables 10 and 11

(see Note 5)

Columns 2 to 4

Table 12

Columns 2 and 3

Cables with minimum spacings in

air as shown and installed—


surface;


perforated or unperforated

trays, cleats or hangers;

(c) in a switchboard or similar

enclosure;

or

24

10 Three-core

cables

Tables 13 and 14

(see Note 5)

Columns 2 to 4

Table 15

Columns 2 and 3 11 (d) suspended from a catenary or as

a self-supported overhead cable. 22

12 Two-core

cables

Tables 10 and 11

(see Note 4)

Columns 5 to 7

Table 12

Columns 4 and 5

Cables installed—

(a) clipped direct to a wall, floor,

ceiling or similar surface;

(b) buried directly in concrete or

masonry above the ground or in

plaster or render on a wall;

(c) in a ventilated trench or open

trunking;

or

(d) in a switchboard or similar

enclosure

22

13 Three-core

cables

Tables 13 and 14

(see Note 4)

Columns 5 to 7

Table 15

Columns 4 and 5

NOTES:


cable.

2 Earthing conductors, lightly loaded neutral conductors of three-phase circuits and conductors subject only

to momentary loading, such as control wiring, shall not be counted in the number of cable cores.

3 See column headings of Tables 4 to 15.

4 See Table 22 for the derating factor applicable to a single circuit fixed to the underside of a ceiling or

similar horizontal surface.

5 See Tables 23 and 24 for the derating factors applicable to a single circuit fixed to perforated or

unperforated trays.

6 See AS/NZS 3000 for the restricted installation conditions of certain types of cable, e.g. unarmoured

cables in plaster or cement render on walls.

TABLE 3(1) (continued)

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TABLE 3(2)



APPLICABLE DERATING TABLES—ENCLOSED

1 2 3 4 5 6

Item

No.

Cable

details

(see Note 1)

Reference drawing

(see Note 2)

Current-carrying

capacity table

reference



carrying capacity (See Note 3)

Derating

table for

more than

one circuit

1 Two single-

core cables

Tables 4 and 5

Columns 15 to 17

Table 6

Columns 11 and 12

Cables in wiring enclosures installed

in—

(a) air;

(b) plaster, cement render, masonry

or concrete in a wall or floor;

(c) a concrete slab on or above the

surface of the ground; or

(d) a ventilated trench.

Cables installed in—

(a) a wiring enclosure on a wall; or

(b) an enclosed trench with a

removable cover.

22 2 Three

single-core

cables

Tables 7 and 8

Columns 15 to 17

Table 9

Columns 11 and 12

3 Two single-

core cables

Tables 4 and 5

Columns 18 and 19

Table 6

Column 13

Cables enclosed or unenclosed—

(a) partially surrounded by thermal

insulation material; or

(b) in an enclosed trench.

22 4 Three

single-core

cables

Tables 7 and 8

Columns 18 and 19

Table 9

Column 13

5 Two single-

core cables

Tables 4 and 5

Columns 20 and 21

Table 6

Column 14

Unenclosed cables completely

surrounded by thermal insulation.

22 6 Three

single-core

cables

Tables 7 and 8

Columns 20 and 21

Table 9

Column 14

(continued)

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1 2 3 4 5 6

Item

No.

Cable

details

(see Note 1)

Reference drawing

(see Note 2)

Current-carrying

capacity table

reference



carrying capacity (See Note 3)

Derating

table for

more than

one circuit

7 Two-core

cables

Tables 10 and 11

Columns 11 to 13

Table 12

Columns 9 and 10

Cables in wiring enclosures installed

in—

(a) air;

(b) plaster, cement render, masonry

or concrete in a wall or floor;

(c) a concrete slab on or above the

surface of the ground; or

(d) a ventilated trench.

Cables installed in—

(a) closed trunking, or wiring

enclosures on a wall; or

(b) an enclosed trench with a

removable cover.

22

8 Three-core

cables

Tables 13 and 14

Columns 11 to 13

Table 15

Columns 9 and 10

9 Two-core

cables

Tables 10 and 11

Columns 15 to 18

Table 12

Column 11

Enclosed or unenclosed cables

partially surrounded by thermal

insulation.

22 10 Three-core

cables

Tables 13 and 14

Columns 15 to 18

Table 15

Column 11

11 Two-core

cables

Tables 10 and 11

Columns 19 to 22

Table 12

Column 12

Enclosed or unenclosed cables

completely surrounded by thermal

insulation.

22 12 Three-core

cables

Tables 13 and 14

Columns 19 to 22

Table 15

Column 12

NOTES:




3 See AS/NZS 3000 for the restricted installation conditions of certain types of cables, e.g. insulated or

insulated and sheathed cables in metallic and non-metallic conduits.

TABLE 3(2) (continued)

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TABLE 3(3)



APPLICABLE DERATING TABLES—BURIED DIRECT IN THE GROUND

1 2 3 4 5 6

Item

No.

Cable

details

(see Note 1)

Reference drawing

(see Note 2)

Current-carrying

capacity table

reference



carrying capacity (see Note 3)

Derating

table for

more than

one circuit

1 Two single-

core cables

Tables 4 and 5

Columns 22 and 23

Table 6

Column 15

Cables with a minimum depth of

laying of—

(a) 0.3 m under continuous

concrete paved areas; or

(b) 0.5 m in other locations.

25(1) 2 Three

single-core

cables

Tables 7 and 8

Columns 22 and 23

Table 9

Column 15

3 Two-core

cables

Tables 10 and 11

Columns 23 and 24

Table 12

Column 13 25(2)

4 Three-core

cables

Tables 13 and 14

Columns 23 and 24

Table 15

Column 13

NOTES:




3 See Tables 27 and 28 for rating factors applicable to different ambient soil temperatures and depths of

laying.

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TABLE 3(4)



APPLICABLE DERATING TABLES—UNDERGROUND WIRING ENCLOSURES

1 2 3 4 5 6

Item

No.

Cable

details

(see Note 1)

Reference drawing

(see Note 2)

Current-carrying

capacity table

reference

Methods of installation

for cables deemed to

have the same current-

carrying capacity

(see Note 3)

Derating table for

more than one circuit

in same

enclosure

in separate

enclosures

1 Two single-

core cables

Tables 4 and 5

Columns 24 to 26

Table 6

Columns 16 and 17

Cables in a single

enclosure laid—

(a) a minimum of

0.3 m below

continuous

concrete paved

areas; or

(b) minimum 0.5 m in

other locations.

22

26(2)

2 Three

single-core

cables

Tables 7 and 8

Columns 24 to 26

Table 9

Columns 16 and 17

3 One two-

core cable

Tables 10 and 11

Columns 25 to 27

Table 12

Columns 14 and 15

4 One three-

core cable

Tables 13 and 14

Columns 25 to 27

Table 15

Column 14 and 15

5 Single-core

cables

Tables 4 and 5

Columns 27 and 28

Table 6

Column 18

Two enclosures laid—

(a) directly under

continuous concrete

paved areas; or


other locations. 26(1)

6

Tables 7 and 8

Columns 27 and 28

Table 9

Column 18

Three enclosures laid—

(a) directly under

continuous concrete

paved areas; or


other locations.

NOTES:




3 See Tables 27 and 28 for rating factors applicable to different ambient soil temperatures and depths of

laying.

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TABLE 4

CURRENT-CARRYING CAPACITIES

CABLE TYPE: TWO SINGLE-CORE (See Note 1)

INSULATION TYPE: THERMOPLASTIC (See Note 2)

MAXIMUM CONDUCTOR

TEMPERATURE:

75°C

REFERENCE AMBIENT

TEMPERATURE:

40°C IN AIR, 25°C IN GROUND

1 2 3 4 5 6 7 8 9 10 11 12 13

Conductor

size

Current-carrying capacity, A

Unenclosed

Spaced Spaced from surface Touching Exposed to sun

Cu

Al

Cu

Al

Cu

Al

Cu

Al

mm2

Solid/

Stranded

Flexible Solid/

Stranded

Flexible Solid/

Stranded

Flexible Solid/

Stranded

Flexible

1

1.5

2.5

16

21

30

17

21

29

—

—

—

16

21

29

17

21

28

—

—

—

13

16

23

13

17

22

—

—

—

8

10

13

8

10

13

—

—

—

4

6

10

40

51

69

38

49

69

—

—

—

39

49

67

38

48

67

—

—

—

31

40

54

30

38

54

—

—

—

18

22

30

17

21

29

—

—

—

16

25

35

92

124

153

91

121

150

72

96

119

89

119

145

88

115

143

69

92

113

72

97

119

71

94

117

56

75

92

39

50

61

38

49

59

30

39

47

50

70

95

187

238

295

189

238

287

145

184

229

177

223

276

179

224

269

137

173

214

146

184

230

147

185

223

113

143

178

72

89

107

73

89

104

56

69

83

120

150

185

344

395

459

341

393

450

267

307

357

321

367

424

317

365

416

249

285

331

267

308

358

265

306

351

208

239

279

122

137

154

120

135

150

95

106

120

240

300

400

549

636

744

541

624

752

427

495

583

505

582

676

498

571

682

394

456

535

428

495

577

422

486

583

334

388

456

177

198

221

173

192

218

138

155

175

500

630

867

1014

876

1036

685

808

780

897

787

914

624

730

668

770

675

785

535

627

245

269

240

266

196

219

(continued)

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14 15 16 17 18 19 20 21 22 23 24 25 26 27 28

Conductor

size


Enclosed Thermal insulation Buried direct Underground wiring enclosure

Wiring enclosure in air Partially

surrounded by

thermal

insulation

Completely

surrounded by

thermal

insulation

Cu

Al Cu Al Cu Al Cu Al

Cu

Al Cu Al

mm2

Solid/

Stranded Flexible

Solid/

StrandedFlexible

1

1.5

2.5

13

18

24

14

18

24

—

—

—

11

14

20

—

—

—

6

8

12

—

—

—

18

23

32

—

—

—

18

23

32

19

23

31

—

—

—

21

26

36

—

—

—

4

6

10

32

41

54

31

40

54

—

—

—

25

33

44

—

—

—

16

20

27

—

—

—

41

52

69

—

—

—

41

52

69

40

50

68

—

—

—

47

58

77

—

—

—

16

25

35

70

94

112

69

91

110

54

73

87

56

75

90

43

58

70

36

48

59

28

37

46

122

158

190

95

123

147

89

116

139

87

112

136

69

90

108

99

129

155

77

100

120

50

70

95

138

170

212

139

169

206

107

132

164

110

136

169

86

105

131

—

—

—

—

—

—

225

277

332

174

215

257

168

206

252

168

205

244

130

160

195

186

228

278

145

177

215

120

150

185

242

282

320

237

278

312

188

219

249

193

225

256

150

175

199

—

—

—

—

—

—

378

424

480

294

329

374

287

329

373

282

324

363

223

255

291

316

354

408

245

274

317

240

300

400

381

—

—

373

—

—

298

—

—

305

—

—

238

—

—

—

—

—

—

—

—

556

628

713

434

491

564

438

496

575

429

493

572

342

388

454

472

546

621

368

425

487

500

630

—

—

—

—

—

—

—

—

—

—

—

—

—

—

805

904

644

737

649

750

663

754

520

611

721

816

570

652

NOTES:

1 Applies to non-armoured, sheathed or unsheathed cables.


wiring, are based on a conductor temperature of 75°C. This is due to the risk of thermal deformation of

insulation if the cables are clipped, fixed or otherwise installed in a manner which exposes the cable to





used in—

(a) locations where the ambient temperature exceeds the normal 40°C, e.g. equipment wiring in



3 Refer to Tables 3(1), 3(2), 3(3) and 3(4) for cable configurations deemed to have the same current-

carrying capacities as those illustrated.

4 Derating factors may apply as follows:

(a) The current-carrying capacities apply to single circuits. For grouped cable circuits, see

Clause 3.5.2 and Tables 22, 23, 25 and 26 for appropriate derating factors.

TABLE 4 (continued)

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(b) For a single circuit fixed to the underside of a ceiling or similar horizontal surface, see Table 22

for the derating factor to be applied to the current-carrying capacities given in Columns 8 to 10.

(c) For a single circuit fixed to perforated or unperforated cable tray, see Table 23 for the derating

factor to be applied to the current-carrying capacities given in Columns 5 to 7.

(d) For ambient temperature and depth of laying factors, see Tables 27 and 28.

5 To calculate the single-phase voltage drop of these configurations, multiply the appropriate three-phase

voltage drop value in Table 40, Table 43 or Table 46 by 1.155.

6 These ratings are based on 40°C ambient air temperature and 25°C ambient soil temperature. For other

conditions, see Clause 3.5.3.

7 For conductor sizes up to 10mm2 in Column 22 the values are based on ratings for wiring in underground

wiring enclosures.

8 Cables within the scope of AS/NZS 5000.2 (up to 16 mm2) may be rated to the values in the Tables

covering 90°C insulated cables, subject to—

(a) information provided in Note 2; and

(b) any other relevant requirements of AS/NZS 3000.

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TABLE 5



INSULATION TYPES: X-90, X-HF-90, R-EP-90, R-CPE-90, R-HF-90 OR R-CSP-90

MAXIMUM CONDUCTOR

TEMPERATURE:

90°C (See Note 2)

REFERENCE AMBIENT

TEMPERATURE:


1 2 3 4 5 6 7 8 9 10 11 12 13

Conductor

size


Unenclosed


Cu

Al

Cu

Al

Cu

Al

Cu

Al

mm2

Solid/

Stranded Flexible

Solid/

StrandedFlexible

Solid/

StrandedFlexible

Solid/

Stranded Flexible

1

1.5

2.5

20

26

36

21

26

35

—

—

—

20

25

36

21

26

34

—

—

—

16

20

28

16

20

27

—

—

—

12

15

21

13

16

21

—

—

—

4

6

10

48

61

84

46

59

83

—

—

—

47

60

82

46

58

81

—

—

—

37

47

65

36

46

64

—

—

—

28

36

48

27

34

48

—

—

—

16

25

35

112

151

186

110

147

183

87

117

144

108

145

177

106

141

174

84

112

137

86

117

144

85

114

141

67

91

111

64

86

105

63

83

103

50

66

81

50

70

95

228

291

361

231

292

351

177

226

280

216

273

338

218

274

328

167

212

262

176

224

278

178

225

271

136

174

216

127

160

197

128

161

192

99

124

153

120

150

185

422

486

565

418

483

555

328

377

439

393

451

522

389

448

512

305

350

406

325

375

436

322

373

428

253

291

340

229

262

303

226

260

296

178

204

236

240

300

400

678

787

923

668

772

933

527

612

723

622

718

836

613

705

843

485

562

660

522

605

708

515

594

715

408

473

559

359

413

478

353

404

480

280

323

377

500

630

1078

1261

1090

1288

850

1003

966

1113

975

1135

772

904

821

950

830

969

656

772

550

629

552

639

439

511

(continued)

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14 15 16 17 18 19 20 21 22 23 24 25 26 27 28

Conductor

size




surrounded by

thermal

insulation

Completely

surrounded by

thermal

insulation

Cu


Cu

Al Cu Al

mm2

Solid/

Stranded Flexible

Solid/

StrandedFlexible

1

1.5

2.5

16

21

30

17

21

28

—

—

—

13

16

24

—

—

—

8

10

14

—

—

—

20

26

36

—

—

—

20

26

36

21

26

35

—

—

—

24

30

41

—

—

—

4

6

10

38

47

65

37

46

64

—

—

—

30

38

52

—

—

—

19

24

32

—

—

—

46

58

78

—

—

—

46

58

78

45

56

77

—

—

—

53

66

87

—

—

—

16

25

35

84

113

135

82

109

132

65

87

105

67

90

108

52

70

84

43

58

72

33

45

56

139

179

215

107

139

167

100

131

157

98

127

154

78

102

122

112

146

175

87

114

136

50

70

95

166

204

255

167

204

248

129

159

198

133

164

204

103

127

158

—

—

—

—

—

—

255

313

375

198

243

291

189

233

285

190

232

276

147

181

221

211

258

309

164

200

239

120

150

185

292

329

387

286

336

377

226

255

301

233

263

309

181

204

241

—

—

—

—

—

—

427

480

543

332

372

423

325

365

423

319

368

412

252

283

329

358

401

463

278

311

359

240

300

400

461

—

—

452

—

—

360

—

—

369

—

—

288

—

—

—

—

—

—

—

—

630

711

808

492

556

638

497

562

653

486

548

650

388

440

516

536

620

706

417

482

553

500

630

—

—

—

—

—

—

—

—

—

—

—

—

—

—

913

1026

729

833

739

856

733

860

590

695

800

930

632

740

NOTES:



wiring, is based on a conductor temperature of 75°C. This is due to the risk of thermal deformation of





severe mechanical pressure at temperatures higher than 75°C. Such applications also allow for cables to

be used in—

(a) locations where the ambient temperatures exceed the normal 40°C, e.g. equipment wiring in



3 For cables with a maximum conductor temperature of 105°C the applicable current ratings are those

provided for copper conductors up to and including 10mm2 size.



TABLE 5 (continued)

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voltage drop value in Table 40 or Table 43 by 1.155.



8 For conductor sizes up to 10 mm2 in Column 22, the values are based on ratings for wiring in underground

wiring enclosures.

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TABLE 6



INSULATION TYPES: R-HF-110, R-E-110 OR X-HF-110

MAXIMUM CONDUCTOR

TEMPERATURE:

110°C

REFERENCE AMBIENT

TEMPERATURE:


1 2 3 4 5 6 7 8 9

Conductor

size


Unenclosed


Cu Cu Cu Cu

mm2

Solid/

Stranded Flexible

Solid/

StrandedFlexible

Solid/

StrandedFlexible

Solid/

Stranded Flexible

1

1.5

2.5

25

32

45

26

32

43

24

31

44

26

32

42

20

25

36

21

26

34

17

21

30

18

22

29

4

6

10

59

75

103

57

73

102

58

73

99

56

70

98

47

59

81

45

57

80

39

50

68

38

48

67

16

25

35

137

183

225

135

178

221

131

175

214

129

170

210

107

143

176

105

139

172

89

119

146

88

116

143

50

70

95

276

349

434

279

351

422

261

328

406

263

329

395

215

272

339

218

273

329

178

224

277

179

224

269

120

150

185

505

581

673

500

577

660

471

540

624

466

536

611

394

454

527

390

450

516

321

369

427

318

366

418

240

300

400

806

934

1094

794

916

1105

743

857

998

732

841

1006

630

730

853

621

716

860

508

586

682

500

575

687

500

630

1278

1498

1290

1529

1155

1334

1164

1359

990

1146

999

1168

789

909

794

925

(continued)

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41 AS/NZS 3008.1.1:2009

COPYRIGHT

10 11 12 13 14 15 16 17 18

Conductor

size



Wiring enclosure in

air

Partially

surrounded by

thermal

insulation

Completely

surrounded by

thermal

insulation

Cu

Cu Cu Cu

Cu

Cu

mm2

Solid/

Stranded Flexible

Solid/

StrandedFlexible

1

1.5

2.5

20

25

35

21

25

33

16

20

28

10

13

18

23

29

40

23

29

40

24

30

39

26

33

46

4

6

10

46

58

78

45

56

77

37

46

62

23

30

40

53

66

88

53

66

88

51

64

86

59

74

97

16

25

35

104

137

165

102

133

167

83

109

132

53

72

88

154

198

238

115

148

177

112

143

176

127

163

195

50

70

95

205

255

321

207

263

312

164

204

257

—

—

—

282

346

416

214

262

321

215

266

312

236

288

352

120

150

185

369

430

493

364

426

481

296

344

394

—

—

—

473

531

601

366

420

477

359

414

464

400

448

517

240

300

400

594

—

—

583

—

—

476

—

—

—

—

—

698

789

898

561

648

738

548

631

734

600

694

790

500

630

—

—

—

—

—

—

—

—

1018

1148

837

973

855

977

921

1045

NOTES:








for the derating factor to be applied to the current-carrying capacities given in Columns 6 and 7.


factor to be applied to the current-carrying capacities given in Columns 4 and 5.


4 To determine the single-phase voltage drop of these configurations, refer to the appropriate value in Table

40, Table 41 or Table 46.



6 For conductor sizes up to 10 mm2 in Column 15, the values are based on ratings for wiring in underground

wiring enclosures.

TABLE 6 (continued)

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TABLE 7


CABLE TYPE: THREE SINGLE-CORE (See Note 1)


MAXIMUM CONDUCTOR

TEMPERATURE:

75°C

REFERENCE AMBIENT

TEMPERATURE:


1 2 3 4 5 6 7 8 9 10 11 12 13

Conductor

size


Unenclosed


Cu

Al

Cu

Al

Cu

Al

Cu

Al

mm2

Solid/

Stranded Flexible

Solid/

StrandedFlexible

Solid/

StrandedFlexible

Solid/

Stranded Flexible

1

1.5

2.5

16

20

29

16

21

27

—

—

—

14

17

25

14

18

24

—

—

—

13

16

23

13

17

22

—

—

—

8

10

13

8

10

13

—

—

—

4

6

10

38

49

67

37

47

66

—

—

—

33

42

58

32

41

57

—

—

—

31

40

54

30

38

54

—

—

—

18

22

30

17

21

29

—

—

—

16

25

35

89

120

148

88

117

145

69

93

115

77

103

127

75

100

125

59

80

98

72

97

119

71

94

117

56

75

92

39

50

61

38

49

59

30

39

47

50

70

95

181

230

287

183

231

279

141

179

222

156

197

246

157

198

239

121

153

191

146

184

230

147

185

223

113

143

178

72

89

107

73

89

104

56

69

83

120

150

185

335

385

447

331

383

438

260

298

347

287

330

383

284

328

376

223

256

299

267

308

357

264

305

350

208

239

278

122

137

154

120

135

149

95

106

120

240

300

400

535

620

726

528

609

734

417

483

570

457

529

615

451

519

621

358

415

488

426

492

573

420

484

578

334

387

455

176

197

219

172

191

216

138

155

175

500

630

846

990

855

1011

669

789

710

817

717

833

571

668

661

760

668

775

532

622

242

265

237

262

196

219

(continued)

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14 15 16 17 18 19 20 21 22 23 24 25 26 27 28

Conductor

size




surrounded by

thermal

insulation

Completely

surrounded by

thermal

insulation

Cu


Cu

Al Cu Al

mm2

Solid/

Stranded Flexible

Solid/

StrandedFlexible

1

1.5

2.5

12

15

21

13

15

20

—

—

—

10

12

17

—

—

—

6

8

12

—

—

—

16

20

27

—

—

—

16

20

27

16

20

26

—

—

—

19

24

33

—

—

—

4

6

10

28

35

47

27

34

46

—

—

—

23

28

37

—

—

—

16

20

27

—

—

—

36

45

59

—

—

—

36

45

59

35

43

58

—

—

—

43

53

70

—

—

—

16

25

35

62

81

100

61

78

98

48

63

78

50

64

80

39

50

62

36

48

59

28

38

46

104

134

160

81

104

124

78

100

122

76

97

119

60

78

94

90

117

140

70

91

108

50

70

95

119

152

183

120

152

178

92

118

142

95

122

147

74

94

114

—

—

—

—

—

—

190

233

279

147

181

216

144

180

217

145

180

210

112

140

168

168

205

250

131

159

194

120

150

185

217

244

284

213

241

277

169

190

222

173

195

227

135

152

177

—

—

—

—

—

—

317

356

402

247

276

313

252

283

325

247

279

316

196

220

253

283

317

365

220

246

284

240

300

400

331

388

442

336

379

461

269

305

351

265

311

353

207

244

281

—

—

—

—

—

—

465

524

593

364

412

471

377

434

492

376

423

504

295

341

391

422

488

553

329

380

434

500

630

523

588

520

592

421

481

418

471

337

385

—

—

—

—

668

748

537

612

571

639

566

641

459

523

641

723

507

578

NOTES:









be used in—









TABLE 7 (continued)

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5 To determine the three-phase voltage drop of these configurations, refer to the appropriate value in

Table 40, Table 41, Table 43, Table 44 or Table 46.



7 For conductor sizes up to 10mm2 in Column 22, the values are based on ratings for wiring in underground

wiring enclosures.

8 Cables within the scope of AS/NZS 5000.2 (up to 16 mm2) may be rated to the values in the Tables




A1

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TABLE 8




MAXIMUM CONDUCTOR

TEMPERATURE:

90°C AND 105°C (See Note 2)

REFERENCE AMBIENT

TEMPERATURE:


1 2 3 4 5 6 7 8 9 10 11 12 13

Conductor

size


Unenclosed


Cu

Al

Cu

Al

Cu

Al

Cu

Al

mm2

Solid/

Stranded Flexible

Solid/

StrandedFlexible

Solid/

StrandedFlexible

Solid/

Stranded Flexible

1

1.5

2.5

19

25

35

20

25

33

—

—

—

16

21

30

17

22

29

—

—

—

16

20

28

16

20

27

—

—

—

12

15

21

13

16

21

—

—

—

4

6

10

46

59

81

45

57

80

—

—

—

40

50

69

38

49

69

—

—

—

37

47

65

36

46

64

—

—

—

28

36

48

27

34

48

—

—

—

16

25

35

108

146

180

106

142

177

84

113

140

92

125

154

91

121

151

71

97

119

86

117

144

85

114

141

67

91

111

64

86

105

63

83

103

50

66

81

50

70

95

221

282

350

223

283

341

171

219

271

188

240

298

191

241

290

146

186

232

176

224

278

178

225

271

136

174

216

127

160

197

128

161

192

99

124

153

120

150

185

410

472

560

406

470

540

318

366

427

349

403

468

346

400

459

271

313

365

325

375

435

322

372

427

253

291

339

229

262

302

226

260

296

178

203

235

240

300

400

660

766

899

651

752

909

513

596

705

560

648

756

553

637

764

438

508

599

521

602

702

514

591

709

407

472

557

358

410

474

352

402

477

280

322

376

500

630

1051

1230

1062

1256

829

978

874

1010

884

1030

703

824

812

938

821

956

652

765

544

621

546

630

437

507

(continued)

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AS/NZS 3008.1.1:2009 46

COPYRIGHT

14 15 16 17 18 19 20 21 22 23 24 25 26 27 28

Conductor

size




surrounded by

thermal

insulation

Completely

surrounded by

thermal

insulation

Cu


Cu

Al Cu Al

mm2

Solid/

Stranded Flexible

Solid/

StrandedFlexible

1

1.5

2.5

15

18

25

15

19

24

—

—

—

12

15

20

—

—

—

8

10

14

—

—

—

18

22

31

—

—

—

18

22

31

19

23

30

—

—

—

22

27

38

—

—

—

4

6

10

33

42

56

31

41

55

—

—

—

26

34

45

—

—

—

19

24

32

—

—

—

40

50

67

—

—

—

40

50

67

38

49

66

—

—

—

49

60

79

—

—

—

16

25

35

72

97

120

73

94

118

56

75

93

58

77

96

45

60

75

43

58

72

33

45

56

117

151

180

91

117

140

86

113

137

85

109

134

66

87

106

101

132

158

79

103

122

50

70

95

143

183

220

144

183

214

111

142

171

114

146

176

89

114

137

—

—

—

—

—

—

214

262

313

166

203

243

163

203

244

163

203

237

126

158

190

190

232

276

147

180

214

120

150

185

261

295

335

256

291

334

203

229

261

209

236

268

162

183

209

—

—

—

—

—

—

356

400

452

277

310

352

284

320

363

279

316

357

221

249

283

320

358

413

248

277

321

240

300

400

399

469

534

391

458

533

312

368

424

320

375

427

250

294

339

—

—

—

—

—

—

523

589

668

409

463

530

426

491

557

416

479

554

333

385

442

477

552

626

371

430

491

500

630

633

714

630

719

509

583

506

571

407

466

—

—

—

—

752

843

604

688

648

727

642

729

520

593

707

820

559

654

NOTES:









be used in—




3 For cables with a maximum conductor temperature of 105°C, the applicable current ratings are those




TABLE 8 (continued)

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Table 40, Table 41, Table 43, Table 44 or Table 46.




wiring enclosures.

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TABLE 9




MAXIMUM CONDUCTOR

TEMPERATURE:

110°C

REFERENCE AMBIENT

TEMPERATURE:


1 2 3 4 5 6 7 8 9

Conductor

size


Unenclosed


Cu Cu Cu Cu

mm2

Solid/

Stranded Flexible

Solid/

StrandedFlexible

Solid/

StrandedFlexible

Solid/

Stranded Flexible

1

1.5

2.5

24

31

43

25

31

42

21

27

38

22

27

36

20

25

36

21

26

34

17

21

30

18

22

29

4

6

10

57

73

99

55

70

99

50

63

86

48

61

85

47

59

81

45

57

80

39

50

68

38

48

67

16

25

35

132

177

218

130

173

214

114

153

188

112

149

184

107

143

176

105

139

172

89

119

146

88

116

143

50

70

95

267

339

422

270

340

410

230

291

363

233

292

353

215

272

339

217

273

329

178

224

277

179

224

269

120

150

185

492

565

656

487

562

644

422

486

564

418

482

553

394

453

526

390

450

516

321

368

426

317

365

417

240

300

400

786

912

1069

775

895

1079

674

780

910

665

766

918

629

727

847

620

714

855

507

584

678

499

572

682

500

630

1248

1462

1260

1493

1053

1217

1064

1240

981

1132

990

1154

782

898

786

913

(continued)

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10 11 12 13 14 15 16 17 18

Conductor

size



Wiring enclosure in

air

Partially

surrounded by

thermal

insulation

Completely

surrounded by

thermal

insulation

Cu

Cu Cu Cu

Cu

Cu

mm2

Solid/

Stranded Flexible

Solid/

StrandedFlexible

1

1.5

2.5

17

22

32

18

23

31

14

18

25

10

13

18

20

25

36

20

25

36

21

26

34

24

30

42

4

6

10

41

51

71

40

50

70

33

41

57

23

30

40

46

57

77

46

57

77

44

55

76

54

67

88

16

25

35

93

125

151

91

121

148

74

100

121

53

72

88

130

168

201

99

130

155

97

125

151

115

148

176

50

70

95

182

234

285

190

234

277

146

187

228

—

—

—

237

291

348

184

230

277

188

229

268

212

259

315

120

150

185

337

382

449

331

378

438

269

306

359

—

—

—

396

445

503

322

362

415

316

357

404

357

400

461

240

300

400

548

626

718

538

612

757

439

501

575

—

—

—

583

657

746

492

556

631

481

542

648

533

617

700

500

630

865

983

864

993

692

787

—

—

843

947

736

827

729

828

815

920

NOTES:








for the derating factor to be applied to the current-carrying capacities given in Columns 6 and 7.


factor to be applied to the current-carrying capacities given in Columns 4 and 5.



Table 40, Table 41 or Table 46.




wiring enclosures.

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TABLE 10


CABLE TYPE: TWO-CORE SHEATHED (See Note 1)


MAXIMUM CONDUCTOR

TEMPERATURE:

75°C

REFERENCE AMBIENT

TEMPERATURE:


1 2 3 4 5 6 7 8 9 10 11 12 13

Conductor

size


Unenclosed Enclosed

Spaced Touching Exposed to sun Wiring enclosure in air

Cu

Al

Cu

Al

Cu

Al

Cu

Al

mm2

Solid/

Stranded Flexible

Solid/

StrandedFlexible

Solid/

StrandedFlexible

Solid/

Stranded Flexible

1

1.5

2.5

15

19

27

16

20

26

—

—

—

14

18

26

15

18

25

—

—

—

11

14

20

12

14

19

—

—

—

13

16

23

13

17

23

—

—

—

4

6

10

37

46

64

35

45

63

—

—

—

34

44

60

33

42

59

—

—

—

27

34

46

26

32

45

—

—

—

30

39

52

29

38

51

—

—

—

16

25

35

85

113

139

83

110

137

66

88

108

80

107

131

78

104

128

62

83

101

60

79

97

59

77

94

47

62

75

68

90

112

68

87

109

52

70

87

50

70

95

170

215

265

171

215

257

132

167

205

159

201

248

161

202

241

124

156

192

116

145

175

117

145

170

90

112

136

133

170

204

134

169

198

103

132

158

120

150

185

307

351

403

304

348

395

239

272

314

288

328

377

285

326

370

224

255

294

202

227

258

199

225

252

157

177

201

241

271

313

236

267

305

187

210

244

240

300

400

477

547

631

470

537

636

373

429

500

446

511

589

439

502

593

349

401

467

300

339

384

294

331

384

235

266

305

364

424

482

368

415

500

285

333

383

500 716 728 575 668 678 536 429 431 345 561 564 451

(continued)

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14 15 16 17 18 19 20 21 22 23 24 25 26 27

Conductor

size


Thermal insulation Buried direct Underground wiring

enclosure

Partially

surrounded by

thermal

insulation,

unenclosed

Partially

surrounded by

thermal

insulation, in

a wiring

enclosure

Completely

surrounded by

thermal

insulation,

unenclosed

Completely

surrounded by

thermal

insulation, in

a wiring

enclosure

Cu Al Cu Al Cu Al Cu Al Cu Al

Cu

Al mm2 Solid/

Stranded Flexible

1

1.5

2.5

11

14

20

—

—

—

10

13

19

—

—

—

7

9

13

—

—

—

6

8

12

—

—

—

17

21

30

—

—

—

17

21

30

18

22

29

—

—

—

4

6

10

27

35

48

—

—

—

24

31

42

—

—

—

17

22

30

—

—

—

15

20

26

—

—

—

39

50

66

—

—

—

39

50

66

38

48

65

—

—

—

16

25

35

64

85

105

49

66

81

54

72

90

42

56

70

40

53

65

31

41

51

34

45

56

26

35

43

114

147

178

88

114

138

86

112

136

85

108

133

66

87

106

50

70

95

127

161

198

99

125

154

107

136

163

83

105

127

—

—

—

—

—

—

—

—

—

—

—

—

211

259

311

163

201

241

162

202

243

163

202

236

126

157

189

120

150

185

230

263

302

179

204

235

192

217

250

150

168

195

—

—

—

—

—

—

—

—

—

—

—

—

355

398

449

276

309

350

282

317

363

277

313

353

220

246

283

240

300

400

357

409

471

279

321

373

291

340

386

228

266

306

—

—

—

—

—

—

—

—

—

—

—

—

520

586

663

406

460

526

421

483

548

419

472

560

329

379

434

500 534 429 449 360 — — — — 741 595 628 629 504

NOTES:

1 Applies to cables with or without earth core, armoured or unarmoured, including neutral screened cables.








used in—









TABLE 10 (continued)

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(c) For a single circuit fixed to unperforated cable tray, see Table 24 for the derating factor to be

applied to the current-carrying capacities given in Columns 2 to 4.







wiring enclosures.

8 Cables within the scope of AS/NZS 5000 (up to 25 mm2 and with a maximum permissible conductor

operating temperature of not less than 90°C) may be rated to the values in the Table 11 covering 90°C

insulated cables, subject to—



Refer to Paragraph C3 of AS/NZS 3000 for details on simplified protective device selection (MCBs) for

overload protection.

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TABLE 11




MAXIMUM CONDUCTOR

TEMPERATURE:


REFERENCE AMBIENT

TEMPERATURE:


1 2 3 4 5 6 7 8 9 10 11 12 13

Conductor

size


Unenclosed Enclosed


Cu

Al

Cu

Al

Cu

Al

Cu

Al

mm2

Solid/

Stranded Flexible

Solid/

StrandedFlexible

Solid/

StrandedFlexible

Solid/

Stranded Flexible

1

1.5

2.5

18

24

34

19

24

32

—

—

—

17

22

31

18

23

30

—

—

—

15

19

27

16

20

26

—

—

—

16

20

28

16

20

27

—

—

—

4

6

10

45

57

78

43

55

78

—

—

—

42

53

73

40

51

72

—

—

—

36

46

63

35

44

62

—

—

—

37

46

63

35

44

62

—

—

—

16

25

35

104

140

173

103

136

169

81

109

134

97

131

162

96

128

158

75

102

125

83

111

136

82

108

134

64

86

106

82

110

132

80

106

129

63

85

102

50

70

95

211

268

331

213

269

322

163

208

257

197

250

309

199

251

300

153

194

239

165

208

255

167

209

248

128

162

198

162

200

250

163

207

242

126

155

194

120

150

185

385

441

509

381

438

499

299

342

396

359

411

473

355

408

464

279

319

369

295

336

385

292

333

377

230

261

300

285

332

377

289

328

375

222

257

293

240

300

400

604

694

804

596

682

811

472

544

636

562

645

745

554

633

751

439

505

590

454

518

594

446

507

597

354

406

470

448

523

596

439

511

595

350

410

472

500 915 932 734 848 862 680 671 679 538 695 699 557

(continued)

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14 15 16 17 18 19 20 21 22 23 24 25 26 27

Conductor

size



enclosure

Partially

surrounded by

thermal

insulation,

unenclosed

Partially

surrounded by

thermal

insulation, in

a wiring

enclosure

Completely

surrounded by

thermal

insulation,

unenclosed

Completely

surrounded by

thermal

insulation, in

a wiring

enclosure


Cu

Al mm2 Solid/

Stranded Flexible

1

1.5

2.5

14

18

25

—

—

—

12

16

23

—

—

—

9

11

16

—

—

—

8

10

14

—

—

—

19

24

34

—

—

—

19

24

34

20

25

33

—

—

—

4

6

10

33

42

58

—

—

—

29

37

51

—

—

—

21

27

36

—

—

—

18

23

32

—

—

—

45

56

75

—

—

—

45

56

75

43

54

74

—

—

—

16

25

35

78

105

129

60

81

100

66

88

106

51

68

82

49

66

81

38

51

63

41

55

66

32

43

51

132

170

205

102

132

159

98

128

154

95

124

150

75

99

119

50

70

95

158

200

247

122

155

192

130

160

200

101

124

155

—

—

—

—

—

—

—

—

—

—

—

—

244

300

360

189

233

279

185

228

279

186

231

271

144

177

216

120

150

185

287

328

379

223

255

295

228

265

301

177

206

235

—

—

—

—

—

—

—

—

—

—

—

—

410

460

520

319

357

405

318

365

413

318

360

407

247

283

322

240

300

400

449

516

596

351

404

472

358

418

477

280

328

378

—

—

—

—

—

—

—

—

—

—

—

—

603

680

771

471

533

610

485

558

633

475

544

631

379

437

501

500 678 544 556 446 — — — — 862 691 728 729 583

NOTES:

1 Applies to cables with or without earth core, armoured or unarmoured, including neutral screened cables.








used in—









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wiring enclosures.

9 Cables within the scope of AS/NZS 5000 (up to 25 mm2) may be rated to the values in this Table covering

90°C insulated cables, subject to—





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TABLE 12




MAXIMUM CONDUCTOR

TEMPERATURE:

110°C

REFERENCE AMBIENT

TEMPERATURE:


1 2 3 4 5 6 7

Conductor

size


Unenclosed

Spaced Touching Exposed to sun

Cu Cu Cu

mm2

Solid/

Stranded Flexible

Solid/

StrandedFlexible

Solid/

StrandedFlexible

1

1.5

2.5

23

29

41

24

30

40

22

28

39

23

28

38

20

25

36

21

26

34

4

6

10

55

69

95

53

67

94

51

65

89

50

63

88

47

59

81

45

57

80

16

25

35

126

168

206

124

163

202

118

158

194

116

154

190

107

142

174

105

138

170

50

70

95

251

317

392

254

318

381

236

298

367

238

299

357

211

265

326

213

266

317

120

150

185

455

519

598

450

515

586

426

486

559

421

482

547

377

429

491

372

425

481

240

300

400

708

815

941

698

799

949

662

760

878

652

745

884

580

664

763

570

650

767

500 1074 1091 1000 1014 866 877

(continued)

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8 9 10 11 12 13 14 15

Conductor

size


Enclosed Thermal insulation Buried direct Underground wiring

enclosure

Metallic wiring

enclosure in air

Partially

surrounded by

thermal

insulation

Completely

surrounded by

thermal

insulation

Cu

Cu Cu Cu

Cu

mm2

Solid/

StrandedFlexible

Solid/

Stranded Flexible

1

1.5

2.5

19

24

33

20

24

32

15

19

27

11

14

19

22

28

39

22

28

39

23

29

37

4

6

10

45

56

76

43

54

75

36

45

60

26

33

45

51

64

85

51

64

85

49

62

84

16

25

35

102

133

166

100

129

163

81

107

133

59

79

97

145

188

226

111

144

175

109

139

171

50

70

95

200

256

312

202

257

303

160

205

250

—

—

—

268

330

396

208

260

313

209

259

304

120

150

185

368

417

486

362

412

474

294

333

389

—

—

—

452

507

573

363

409

468

357

403

456

240

300

400

588

670

768

577

656

801

470

536

615

—

—

—

665

751

853

554

626

711

541

611

727

500 905 913 724 — 957 819 820

NOTES:

1 Applies to cables with or without earth core, armoured or non-armoured, including neutral screened

cables.





Clause 3.5.2 and Tables 22, 24, 25 and 26 for approximate derating factors.


for the derating factor to be applied to the current-carrying capacities given in Column 4 and 5.


applied to the current-carrying capacities given in Columns 2 and 3.



voltage drop value in Table 42 or Table 48 by 1.155.




wiring enclosures.


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TABLE 13


CABLE TYPES: THREE-CORE AND FOUR-CORE (See Note 1)


MAXIMUM CONDUCTOR

TEMPERATURE:

75°C

REFERENCE AMBIENT

TEMPERATURE:


1 2 3 4 5 6 7 8 9 10 11 12 13

Conductor

size


Unenclosed Enclosed


Cu

Al

Cu

Al

Cu

Al

Cu

Al

mm2

Solid/

Stranded Flexible

Solid/

StrandedFlexible

Solid/

StrandedFlexible

Solid/

Stranded Flexible

1

1.5

2.5

13

16

23

13

17

22

—

—

—

12

15

22

13

16

21

—

—

—

9

12

17

10

12

16

—

—

—

11

14

20

11

14

19

—

—

—

4

6

10

31

40

54

30

38

54

—

—

—

29

37

51

28

36

51

—

—

—

23

29

39

22

28

38

—

—

—

25

33

44

24

32

43

—

—

—

16

25

35

72

97

120

71

94

117

56

75

93

68

91

112

67

89

110

53

71

87

51

67

82

50

65

80

40

52

64

58

76

94

57

73

92

45

59

73

50

70

95

146

185

228

148

185

222

113

143

177

137

172

213

138

173

207

106

134

165

99

123

150

100

123

145

77

96

116

112

142

177

112

142

172

87

111

137

120

150

185

265

303

348

262

301

342

206

235

272

247

282

324

244

280

318

192

219

253

172

194

220

169

192

215

134

151

172

202

228

263

199

229

257

157

177

206

240

300

400

412

472

544

407

464

549

323

372

434

383

438

504

378

430

508

301

345

402

256

288

326

251

282

326

200

227

260

316

—

—

309

—

—

248

—

—

500 616 627 498 571 580 461 363 365 294 — — —

(continued)

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14 15 16 17 18 19 20 21 22 23 24 25 26 27

Conductor

size



enclosure

Partially

surrounded by

thermal

insulation,

unenclosed

Partially

surrounded by

thermal

insulation, in

a wiring

enclosure

Completely

surrounded by

thermal

insulation,

unenclosed

Completely

surrounded by

thermal

insulation, in

a wiring

enclosure


Cu

Al mm2 Solid/

Stranded Flexible

1

1.5

2.5

9

12

17

—

—

—

9

11

16

—

—

—

6

8

11

—

—

—

5

7

10

—

—

—

14

18

25

—

—

—

14

18

25

15

18

24

—

—

—

4

6

10

23

30

41

—

—

—

20

26

35

—

—

—

15

19

25

—

—

—

13

16

22

—

—

—

33

42

55

—

—

—

33

42

55

32

40

54

—

—

—

16

25

35

54

73

90

42

57

69

47

60

75

36

47

58

34

46

56

26

35

43

29

38

47

23

29

36

96

125

150

75

97

117

73

94

114

71

91

112

56

73

89

50

70

95

109

138

170

85

107

132

89

114

142

69

88

110

—

—

—

—

—

—

—

—

—

—

—

—

178

219

263

138

170

204

136

170

208

137

169

201

105

132

161

120

150

185

198

226

259

154

175

203

162

182

211

126

142

165

—

—

—

—

—

—

—

—

—

—

—

—

300

336

379

233

261

296

237

266

304

232

265

296

184

207

237

240

300

400

307

—

—

240

—

—

253

—

—

198

—

—

—

—

—

—

—

—

—

—

—

—

—

—

438

493

557

344

388

444

359

404

468

351

394

467

281

318

374

500 — — — — — — — — 620 501 522 523 422

NOTES:


cables.








used in—










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wiring enclosures.

8 Cables within the scope of AS/NZS 5000 (up to 25 mm2) may be rated to the values in the Table 14






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TABLE 14


CABLE TYPES: THREE-CORE AND FOUR-CORE (See Note 1)


MAXIMUM CONDUCTOR

TEMPERATURE:


REFERENCE AMBIENT

TEMPERATURE:


1 2 3 4 5 6 7 8 9 10 11 12 13

Conductor

size


Unenclosed Enclosed


Cu

Al

Cu

Al

Cu

Al

Cu

Al

mm2

Solid/

Stranded Flexible

Solid/

StrandedFlexible

Solid/

StrandedFlexible

Solid/

Stranded Flexible

1

1.5

2.5

16

20

28

16

20

27

—

—

—

14

19

26

15

19

26

—

—

—

13

16

23

13

17

22

—

—

—

13

16

24

14

17

23

—

—

—

4

6

10

38

48

66

36

46

66

—

—

—

35

45

62

34

43

61

—

—

—

30

39

53

29

37

52

—

—

—

30

38

53

29

37

52

—

—

—

16

25

35

88

119

147

87

116

144

68

93

114

83

111

137

81

108

135

64

86

106

70

94

115

69

92

113

54

73

89

68

91

114

67

89

111

53

71

88

50

70

95

180

229

283

182

230

275

140

178

220

168

213

263

170

214

256

130

165

204

140

177

217

142

177

211

109

137

168

136

173

209

136

173

202

105

134

162

120

150

185

330

377

436

327

375

428

256

293

340

306

350

404

303

348

396

238

272

315

251

285

327

248

283

320

195

222

255

246

277

322

242

274

314

192

216

251

240

300

400

517

594

685

511

584

692

405

467

546

479

549

632

472

539

638

375

432

504

385

439

502

379

430

504

302

345

400

386

—

—

379

—

—

303

—

—

500 779 794 629 718 730 579 566 573 457 — — —

(continued)

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14 15 16 17 18 19 20 21 22 23 24 25 26 27

Conductor

size



enclosure

Partially

surrounded by

thermal

insulation,

unenclosed

Partially

surrounded by

thermal

insulation, in

a wiring

enclosure

Completely

surrounded by

thermal

insulation,

unenclosed

Completely

surrounded by

thermal

insulation, in

a wiring

enclosure


Cu

Al mm2 Solid/

Stranded Flexible

1

1.5

2.5

12

15

21

—

—

—

10

13

19

—

—

—

7

9

13

—

—

—

6

8

12

—

—

—

16

20

29

—

—

—

16

20

29

17

21

28

—

—

—

4

6

10

28

36

49

—

—

—

24

30

42

—

—

—

18

22

31

—

—

—

15

19

26

—

—

—

37

46

63

—

—

—

37

46

63

36

45

62

—

—

—

16

25

35

66

89

110

51

69

85

55

73

91

42

57

71

41

56

69

32

43

53

34

46

57

26

36

44

110

143

172

85

111

133

81

107

130

79

103

127

63

83

101

50

70

95

134

170

210

104

132

163

108

138

167

84

107

129

—

—

—

—

—

—

—

—

—

—

—

—

204

251

302

159

195

234

155

193

233

155

193

226

120

150

181

120

150

185

245

280

323

190

218

252

197

222

257

153

172

201

—

—

—

—

—

—

—

—

—

—

—

—

344

385

435

267

299

340

270

304

348

266

300

339

210

236

272

240

300

400

383

—

—

300

—

—

309

—

—

242

—

—

—

—

—

—

—

—

—

—

—

—

—

—

504

567

640

395

446

510

411

463

524

402

452

537

322

365

417

500 — — — — — — — — 714 577 601 602 485

NOTES:


cables.








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wiring enclosures

9 Cables within the scope of AS/NZS 5000 (up to 25 mm2) may be rated to the values in Table 11 covering

90°C insulated cables, subject to—





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TABLE 15


CABLE TYPES: THREE-CORE AND FOUR-CORE SHEATHED (See Note 1)


MAXIMUM CONDUCTOR

TEMPERATURE:

110°C

REFERENCE AMBIENT

TEMPERATURE:


1 2 3 4 5 6 7

Conductor

size


Unenclosed

Spaced Touching Exposed to sun

Cu Cu Cu

mm2

Solid/

Stranded Flexible

Solid/

StrandedFlexible

Solid/

StrandedFlexible

1

1.5

2.5

20

25

35

21

26

34

18

24

33

19

24

32

17

22

30

18

22

29

4

6

10

47

59

81

45

57

80

44

56

76

42

54

75

40

50

69

39

49

68

16

25

35

107

144

177

106

140

173

101

135

166

99

131

162

91

121

148

89

118

145

50

70

95

216

272

337

218

273

327

202

255

314

204

255

306

180

227

278

182

227

271

120

150

185

391

447

515

387

444

505

364

416

479

360

413

470

322

367

421

318

364

412

240

300

400

611

701

810

602

688

817

567

650

751

559

638

756

496

567

651

488

555

655

500 921 936 852 865 737 746

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8 9 10 11 12 13 14 15

Conductor

size


Enclosed Thermal insulation Buried direct Underground wiring

enclosure

Metallic wiring

enclosure in air

Partially

surrounded by

thermal

insulation

Completely

surrounded by

thermal

insulation

Cu

Cu Cu Cu

Cu

mm2

Solid/

StrandedFlexible

Solid/

Stranded Flexible

1

1.5

2.5

16

20

29

17

21

27

13

16

23

9

12

17

19

24

33

19

24

33

20

24

31

4

6

10

38

47

64

36

46

65

30

38

51

22

28

38

43

53

71

43

53

71

41

51

71

16

25

35

86

116

140

84

112

137

68

93

112

50

67

83

122

158

190

93

122

146

91

118

143

50

70

95

174

217

270

175

217

263

139

173

216

—

—

—

226

277

333

177

217

267

178

217

259

120

150

185

311

360

411

306

356

402

249

288

329

—

—

—

379

426

481

304

346

391

298

341

381

240

300

400

498

—

—

489

—

—

398

—

—

—

—

—

558

629

713

463

522

608

453

509

606

500 — — — — 797 680 680

NOTES:


cables.












Table 42 or Table 48.




wiring enclosures.


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TABLE 16


CABLE TYPE: FLEXIBLE CORDS

INSULATION TYPES: THERMOPLASTIC OR CROSS-LINKED

MAXIMUM CONDUCTOR

TEMPERATURE:

60°C

REFERENCE AMBIENT

TEMPERATURE:

25°C IN AIR

Conductor size

mm2

Current-carrying capacity

A

0.5

0.75

1.0

3 (See Note 2)

7.5

10

1.5

2.5

4.0

16

20

25

NOTES:

1 Where a flexible cord is wound on a drum, multiply current-carrying capacity by the appropriate factor, as

follows:

Number of layers: 1 2 3 4

Derating factor: 0.76 0.58 0.47 0.40

2 Flexible cords having tinsel conductors with a nominal cross-sectional area of 0.5 mm2 have a current-

carrying capacity of 0.5 A.

3 The current-carrying capacity is based on a cable maximum conductor operating temperature of 60°C in

order to limit the surface temperatures for the expected use of such cables. Where flexible cords are used

as installation wiring, the current ratings are given in Tables 4 to 15 and 17. (Refer to Clause 3.3.2).

4 To determine the three-phase voltage drop, refer to the appropriate value in Table 46, Table 47 or

Table 48. To determine the single-phase voltage drop, multiply the three-phase value by 1.155.

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TABLE 17


CABLE TYPES: CABLES AND FLEXIBLE CORDS

INSULATION TYPES: R-S-150, TYPE 150 FIBROUS OR 150°C RATED FLUOROPOLYMER

1 2 3 4 5

Conductor size


Two single-core or one two-core Three or four single-core or

three or four core

Unenclosed in air Enclosed in air Unenclosed in air Enclosed in air

mm2

0.5

0.75

1.0

19

24

28

15

20

23

15

20

24

13

16

19

1.5

2.5

4

37

50

67

28

38

50

31

43

58

24

32

42

6

10

16

87

120

165

67

90

119

74

105

140

55

76

99

25

35

215

265

160

194

185

230

135

163

NOTES:

1 As a conservative alternative to cable manufacturers’ recommendations, the values given in this

Table may also be applied to fibrous or fluoropolymer insulated cables designed for a maximum operating

temperature of 200°C.

2 No values are given in Section 4 for voltage drop for these types of cable as they are generally installed

for relatively short connections to high temperature equipment. However, on longer cable runs, as the

increase in conductor impedance at 150°C is considerable, it may be necessary to take voltage drop into

account.

3 These ratings are based on 40°C ambient air temperature. For other conditions, see Clause 3.5.3.

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TABLE 18


CABLE TYPE: BARE SINGLE-CORE MIMS CABLES WITH COPPER CONDUCTORS

SHEATH

TEMPERATURE:

100°C

1 2 3 4 5 6 7

Conductor

size


Vertical

spaced—

spaced from

wall

Flat

horizontal—

spaced from

wall

Flat vertical—

clipped to wall

Vertical

spaced—

spaced from

wall

Trefoil—

spaced from

wall

Flat vertical—

clipped to wall

mm2

0.6/0.6 kV cables

1

1.5

2.5

4

20

26

35

47

18

23

31

42

16

21

28

38

19

25

34

45

16

21

28

38

15

19

26

35

1/1 kV cables

1.5

2.5

4

30

40

54

27

36

48

24

33

43

29

39

52

22

33

43

22

30

40

6

10

16

68

93

125

62

84

115

55

76

100

66

90

120

55

75

100

50

69

92

25

35

50

165

205

260

150

185

235

135

170

210

160

200

250

135

165

210

125

155

190

70

95

120

325

380

445

295

345

405

265

310

360

315

365

430

265

315

370

240

280

330

150

185

240

520

610

730

470

550

660

420

495

590

500

590

705

430

505

605

385

450

540

300

400

815

1010

735

915

660

820

785

975

690

855

600

745

NOTES:

1 The current-carrying capacities given in this Table are based on a maximum operating temperature of

100°C for the external surface of the bare copper sheath. The current-carrying capacities of served cables

may be 1.1 times higher than these if they are served with a material that is suitable for a copper sheath

temperature of 105°C. See Clause 3.2.2 and Table 1 for conditions, where higher cable operating

temperatures may be permitted for bare sheathed cables.

2 To determine the three-phase voltage drop, refer to the appropriate value in Table 49. To determine the

single-phase voltage drop, multiply the three-phase value by 1.155.

3 The current-carrying capacities apply to single circuits. For grouped cable circuits see—

(a) Clause 3.5.2 and Tables 22 to 26 for derating factors for served cables; and

(b) Clause 3.5.2.2(a) for the treatment of unserved cables.

4 For earth sheath return system, temperature rises could be higher. Refer to manufacturer.


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TABLE 19


CABLE TYPE: BARE MULTICORE MIMS CABLES WITH COPPER CONDUCTORS

SHEATH

TEMPERATURE:

100°C

1 2 3 4 5 6 7

Conductor

size


Two core—

spaced from

wall

Two core—

clipped to wall

Three and four

core—spaced

from wall

Three and four

core—clipped

to wall

Seven core—

spaced from

wall

Seven core—

clipped to wall

mm2

0.6/0.6 kV cables

1

1.5

2.5

4

18

23

32

43

16

21

29

40

15

20

27

—

14

18

26

—

11

15

20

—

10

14

19

—

1/1 kV cables

1.5

2.5

4

27

36

48

25

33

44

22

30

40

21

28

38

16

22

30

15

20

28

6

10

16

61

85

115

57

78

105

51

71

96

48

67

90

—

—

—

—

—

—

25 150 140 125 120 — —

NOTES:

1 The current-carrying capacities given in this Table are based on a maximum operating temperature of

100°C for the external surface of the bare copper sheath. The current-carrying capacities of served cables

may be 1.1 times higher than these if they are served with a material which is suitable for a copper sheath

temperature of 105°C. See Clause 3.2.2 and Table 1 for conditions where higher cable operating

temperatures may be permitted for bare sheathed cables.

2 To determine the three-phase voltage drop, refer to the appropriate value in Table 49. To determine the

single-phase voltage drop, multiply the three-phase value by 1.155.

3 The current-carrying capacities apply to single circuits. For grouped cable circuits see—

(a) Clause 3.5.2 and Tables 22 to 26 for derating factors for served cables; and

(b) Clause 3.5.2.2(a) for the treatment of unserved cables.

4 For earth sheath return system, temperature rises could be higher. Refer to manufacturer.


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TABLE 20


CABLE TYPES: AERIAL CABLES WITH COPPER CONDUCTORS

1 2 3 4 5 6 7 8 9 10

Conductor

size (mm2)

or standing

(No./mm)


Bare conductors PVC insulated

single-core

PVC insulated two-core

twisted, single-core

neutral screened and

two-core or three-core

parallel-webbed cable

Still

air

1 m/s

wind

2 m/s

wind

Still

air

1 m/s

wind

2 m/s

wind

Still

air

1 m/s

wind

2 m/s

wind

7/1.00

6

7/1.25

37

38

49

74

76

97

87

89

115

—

35

—

—

70

—

—

79

—

—

30

—

—

50

—

—

59

—

10

16

7/1.75

53

71

76

105

139

148

123

164

174

48

65

—

96

127

—

109

145

—

40

52

—

68

90

—

80

107

—

7/2.00

25

35

89

96

117

174

186

226

205

220

267

—

88

107

—

167

203

—

191

232

—

68

82

—

120

145

—

142

171

7/2.75

50

19/1.75

133

142

142

257

272

272

303

321

322

—

130

—

—

242

—

—

276

—

—

97

—

—

173

—

—

205

—

19/2.00

70

7/3.50

168

179

181

321

341

345

379

403

407

—

164

—

—

303

—

—

347

—

—

119

—

—

217

—

—

257

—

7/3.75

95

37/1.75

197

216

216

376

410

410

444

484

485

—

198

—

—

360

—

—

413

—

—

—

—

—

—

—

—

—

—

19/2.75

120

19/3.00

251

255

280

474

481

528

560

568

625

—

234

—

—

423

—

—

485

—

—

—

—

—

—

—

—

—

—

150

185

37/2.50

290

336

339

547

628

634

646

742

750

267

311

—

477

543

—

546

622

—

—

—

—

—

—

—

—

—

—

(continued)

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11 12 13 14 15 16 17 18 19 20

Conductor

size (mm2)

or standing

(No./mm)


PVC insulated

three-core and four-core

twisted and two-core,

three-core or four-core

neutral screened cable

XLPE insulated

two-core twisted cable

and ABC

XLPE insulated


twisted cable and ABC

Still

air

1 m/s

wind

2 m/s

wind

Still

air

1 m/s

wind

2 m/s

wind

Still

air

1 m/s

wind

2 m/s

wind

7/1.00

6

7/1.25

—

26

—

—

48

—

—

56

—

—

36

—

—

56

—

—

66

—

—

32

—

—

54

—

—

62

—

10

16

7/1.75

36

47

—

65

85

—

76

100

—

48

64

—

77

101

—

90

119

—

44

58

—

73

96

—

84

111

—

7/2.00

25

35

—

63

76

—

113

136

—

133

160

—

84

—

—

135

—

—

158

—

—

77

—

—

127

—

—

148

—

7/2.75

50

19/1.75

—

92

—

—

163

—

—

192

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

19/2.00

70

7/3.50

—

115

—

—

204

—

—

242

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

7/3.75

95

37/1.75

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

19/2.75

120

19/3.00

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

150

185

37/2.50

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

NOTES:

1 The current-carrying capacities are based on an ambient temperature of 40°C, a maximum conductor

temperature of 75°C and exposure to direct sunlight having an intensity of 1000 W/m2. In addition the

values for bare conductors are based on black (weathered) conductors and the values for insulated

conductors are based on the use of black PVC or XLPE.

2 Under normal circumstances there will always be some air movement and a minimum rating for 1.0 m/s

wind is recommended.

3 To determine the three-phase voltage drop of these configurations, refer to the following Tables:

(a) For twisted cables, see Table 40.

(b) For parallel and webbed cables, see Table 41.

(c) For bare and single insulated cables, see Table 50.



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TABLE 21


CABLE TYPES: AERIAL CABLES WITH ALUMINIUM CONDUCTORS

1 2 3 4 5 6 7 8 9 10

Conductor

size (mm2)

or standing

(No./mm)


Bare conductors PVC insulated

single-core

PVC insulated two-core

twisted, single-core

neutral screened and

two-core or three-core

parallel-webbed cable

Still

air

1 m/s

wind

2 m/s

wind

Still

air

1 m/s

wind

2 m/s

wind

Still

air

1 m/s

wind

2 m/s

wind

16

25

35

56

76

92

109

146

177

128

173

209

49

67

82

97

128

156

111

146

178

41

53

63

71

91

111

84

108

132

7/2.50

7/2.75

50

93

105

111

180

202

214

213

239

252

—

—

99

—

—

186

—

—

213

—

—

75

—

—

134

—

—

158

7/3.00

70

7/3.75

117

141

156

225

268

297

266

317

350

—

126

—

—

233

—

—

267

—

—

92

—

—

167

—

—

158

—

95

7/4.50

120

172

196

200

327

370

378

386

438

447

155

—

180

282

—

326

323

—

374

110

—

—

203

—

—

243

—

—

7/4.75

150

19/3.25

209

228

244

395

429

459

467

507

542

—

206

—

—

367

—

—

420

—

—

—

—

—

—

—

—

—

—

185

19/3.50

264

269

493

503

583

595

239

—

419

—

479

—

—

—

—

—

—

—

(continued)

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11 12 13 14 15 16 17 18 19 20

Conductor

size (mm2)

or standing

(No./mm)


PVC insulated


twisted and two-core,

three-core or four-core

neutral screened cable

XLPE insulated

two-core twisted cable

and ABC

XLPE insulated


twisted cable and ABC

Still

air

1 m/s

wind

2 m/s

wind

Still

air

1 m/s

wind

2 m/s

wind

Still

air

1 m/s

wind

2 m/s

wind

16

25

35

36

48

59

66

87

105

77

101

123

49

64

78

78

103

125

91

121

147

44

59

72

74

97

118

86

113

137

7/2.50

7/2.75

50

—

—

71

—

—

126

—

—

148

—

—

94

—

—

151

—

—

178

—

—

88

—

—

142

—

—

165

7/3.00

70

7/3.75

—

89

—

—

157

—

—

185

—

—

116

—

—

189

—

—

223

—

—

110

—

—

177

—

—

207

—

95

7/4.50

120

108

—

—

191

—

—

229

—

—

141

—

—

231

—

—

274

—

—

136

—

157

216

—

249

257

—

300

7/4.75

150

19/3.25

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

179

—

—

282

—

—

343

—

185

19/3.50

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

NOTES:

1 The current-carrying capacities are based on an ambient air temperature of 40°C, a maximum conductor

temperature of 75°C for PVC or 80°C for XLPE, and exposure to direct sunlight having an intensity of

1000 W/m2. In addition the values for bare conductors are based on black (weathered) conductors and the

values for insulated conductors are based on the use of black PVC or XLPE.

2 Under normal circumstances there will always be some air movement and a minimum rating for 1.0 m/s

wind is recommended.

3 To determine the three-phase voltage drop of these configurations, refer to the following Tables:

(a) For twisted cables, see Table 43.

(b) For parallel and webbed cables, see Table 44.

(c) For bare and single insulated cables, see Table 51.



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TABLE 22

DERATING FACTORS FOR BUNCHED CIRCUITS

CABLE TYPES: SINGLE-CORE AND MULTICORE

INSTALLATION

CONDITIONS:

IN AIR OR IN WIRING ENCLOSURES

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

Item

No.

Arrangement of

cables (see Notes 1 & 2)

Derating factors

Number of circuits

1 2 3 4 5 6 7 8 9 10 12 14 16 18 20 or

more

1 Bunched in air 1.00 0.87 0.75 0.72 0.70 0.67 — — — — — — — — —

2 Bunched on a surface

or enclosed

1.00 0.80 0.70 0.65 0.60 0.57 0.54 0.52 0.50 0.48 0.45 0.43 0.41 0.39 0.38

3 Single layer

on wall or

floor

Touching 1.00 0.85 0.79 0.75 0.73 0.72 0.72 0.71 0.70 0.70 0.70 0.70 0.70 0.70 0.70

4 Spaced

(see Notes

5 & 6)

1.00 0.94 0.90 0.90 0.90 0.90 0.90 0.90 0.90 0.90 0.90 0.90 0.90 0.90 0.90

5 Single layer

under

ceiling

Touching 0.95 0.81 0.72 0.68 0.66 0.64 0.63 0.62 0.61 0.61 0.61 0.61 0.61 0.61 0.61

6 Spaced

(see Notes

5 & 6)

0.95 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85

NOTES:

1 Where the cable in the arrangements shown in Columns 2 and 3 consist of n loaded conductors, the

conductors may be considered as—

(a) 2

n

groups of two loaded conductors; or

(b) 3

n

groups of three loaded conductors.


to momentary loading, such as control wiring, are not taken into account when considering the number of

circuits.

3 These factors are based on uniform groups of cables, equally loaded. In accordance with Clause 3.5.6 the

factors for circuits subject to intermittent or varying loads may be higher.

4 These factors are applicable to numbers of circuits comprising the following:

(a) Groups of two, three or four single-core cables.

(b) Multicore cables.

(c) Cables passing more than once through the same group of cables or wiring enclosures and circuits

connected in parallel in accordance with Clause 3.5.2.7.

5 ‘Spaced’ means a clearance of one cable diameter between cable surfaces of adjacent cables. Where the

cables concerned are not of the same size, the spacing will be based on the largest cable diameter in the

adjacent groups.

6 No derating factor is applicable for the minimum spacings specified in Clause 3.5.2.2 (c) and Figure 1.

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TABLE 23

DERATING FACTORS FOR CIRCUITS

CABLE TYPE: SINGLE-CORE

INSTALLATION

CONDITIONS:

IN TRAYS, RACKS, CLEATS OR OTHER SUPPORTS IN AIR

1 2 3 4 5 6 7 8

Item

No.

Installation Number of tiers

or rows of cable

supports

Arrangements of

cables in a circuit

(see Note 2)

Derating factors

Number of circuits per tier or row

1 2 3

1

Unperforated trays

(See Note 6)

1

2 or 3 cables in

horizontal formation

0.95 0.85 0.84

2 2 0.92 0.83 0.79

3 3 0.91 0.82 0.76

4

Perforated trays

(See Note 6)

1

2 or 3 cables in


0.97 0.89 0.87

5 2 0.94 0.85 0.81

6 3 0.93 0.84 0.79

7

Ladder supports,

racks and cleats

(See Note 6)

1

2 or 3 cables in


1.00 0.95 0.94

8 2 0.95 0.90 0.88

9 3 0.95 0.89 0.85

10

Vertical perforated

trays

(See Note 7)

1

2 or 3 cables in

vertical formation

0.94 0.85 —

11 2 0.92 0.83 —

12

Unperforated trays

(See Note 6)

1

2 or 3 cables in


0.98 0.96 0.94

13 2 0.95 0.91 0.87

14 3 0.94 0.90 0.85

15

Perforated trays

(See Note 6)

1

2 or 3 cables in


1.00 0.98 0.96

16 2 0.97 0.93 0.89

17 3 0.96 0.92 0.86

18

Ladder supports

(See Note 6)

1

2 or 3 cables in


1.00 1.00 1.00

19 2 0.97 0.95 0.93

20 3 0.97 0.94 0.90

21

Vertical perforated

trays

(See Note 7)

1

2 or 3 cables in

vertical formation

1.00 0.91 0.89

22

2

1.00 0.90 0.86

NOTES:

1 D equals the cable outside diameter.


to momentary loading, such as control wiring, shall not be taken into account when considering the

number of circuits.

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3 These derating factors are to be applied to groups of two, three or four single-core cables for which the

current-carrying capacity for a single circuit is obtained from Columns 5 to 7 of Tables 4, 5, 7 and 8,

Columns 4 and 5 of Tables 6 and 9 and Tables 16 to 19. The factors are also applicable to groups of

single-core cables making up parallel circuits in accordance with Clause 3.5.2.7.

4 These factors are based on uniform groups of cables, equally loaded. In accordance with Clause 3.5.6, the

factors for circuits subject to intermittent or varying loads may be higher.

5 These factors are applicable to single layers of cables or trefoil groups, as shown in Column 2. Where

there is more than one layer on the same tray or ladder support, Table 22 may be used.

6 The vertical spacing of horizontal trays and ladder supports shall be not less than 300 mm (see also

Figure 1).

7 The horizontal spacing of vertical trays mounted back-to-back shall be not less than 230 mm.

8 No derating factor is applicable for the minimum spacings specified in Clause 3.5.2.2 (c) and Figure 1(a).

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TABLE 24

DERATING FACTORS FOR CIRCUITS

CABLE TYPE: MULTICORE

INSTALLATION

CONDITIONS:

IN TRAYS, RACKS, CLEATS OR OTHER SUPPORTS IN AIR

1 2 3 4 5 6 7 8 9 10

Item

No.

Installation Number of

tiers or rows

of cable

supports

Derating factors

Number of cables

1 2 3 4 6 9

1

Unperforated

trays

Touching

(see Note 6)

1 0.97 0.85 0.78 0.75 0.71 0.68

2 2 0.97 0.84 0.76 0.73 0.68 0.63

3 3 0.97 0.83 0.75 0.72 0.66 0.61

4

Spaced

(see Note 6)

1 0.97 0.96 0.94 0.93 0.90 —

5 2 0.97 0.95 0.92 0.90 0.86 —

6 3 0.97 0.94 0.91 0.89 0.84 —

7

Perforated trays

Touching

(see Note 6)

1 1.00 0.88 0.82 0.78 0.76 0.73

8 2 1.00 0.87 0.80 0.76 0.73 0.68

9 3 1.00 0.86 0.79 0.75 0.71 0.66

10

Spaced

(see Note 6)

1 1.00 1.00 0.98 0.95 0.91 —

11 2 1.00 0.99 0.96 0.92 0.87 —

12 3 1.00 0.98 0.95 0.91 0.85 —

13

Ladder supports,

racks and cleats

Touching

(see Note 6)

1 1.00 0.87 0.82 0.80 0.79 0.78

14 2 1.00 0.86 0.80 0.78 0.76 0.73

15 3 1.00 0.85 0.79 0.76 0.73 0.70

16

Spaced

(see Note 6)

1 1.00 1.00 1.00 1.00 1.00 —

17 2 1.00 0.99 0.98 0.97 0.96 —

18 3 1.00 0.98 0.97 0.96 0.93 —

19

Vertical

perforated trays

1 1.00 0.88 0.82 0.77 0.73 0.72

20 Touching

(see Note 7) 2 1.00 0.88 0.81 0.76 0.72 0.70

21

1 1.00 0.91 0.89 0.88 0.87 —

22 Spaced

(see Note 7) 2 1.00 0.91 0.88 0.87 0.86 —

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NOTES:


cable.


to momentary loading, such as control wiring, shall not be taken into account when considering the

number of circuits.

3 These derating factors are to be applied to groups of multicore cables for which the current-carrying

capacity for a single circuit is obtained from Columns 2 to 4 of Tables 10, 11, 13 and 14, Columns 2 and 3

of Tables 12 and 15 and Tables 16 to 19. The factors are also applicable to groups of multicore cables

making up parallel circuits in accordance with Clause 3.5.2.7.

4 These factors are applicable to uniform groups of cables, equally loaded. In accordance with Clause 3.5.6

the factors for circuits subject to intermittent or varying loads may be higher.

5 These factors are applicable to single layers of cables as shown in Column 2. Where there is more than

one layer on the same tray or ladder support, Table 22 may be used.

6 The vertical spacing of horizontal trays and ladder supports shall be not less than 300 mm.

7 The horizontal spacing of vertical trays mounted back-to-back shall be not less than 230 mm.

8 No derating factor is applicable for the minimum spacings specified in Clause 3.5.2.2 (c) and Figure 1(b).

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TABLE 25(1)

DERATING FACTORS FOR GROUPS OF CIRCUITS


INSTALLATION

CONDITIONS:

BURIED DIRECT IN GROUND

1 2 3 4 5 6 7

Number of

circuits

Derating factors

Touching Distance (S), m

0.15 0.30 0.45 0.60

Trefoil Laid flat

2

3

4

0.78

0.66

0.61

0.81

0.70

0.64

0.83

0.73

0.68

0.88

0.79

0.74

0.91

0.84

0.81

0.93

0.87

0.85

5

6

7

0.56

0.53

0.50

0.60

0.57

0.54

0.64

0.61

0.59

0.73

0.71

0.69

0.79

0.78

0.76

0.83

0.82

0.82

8

9

10

0.49

0.47

0.46

0.53

0.51

0.50

0.57

0.56

0.55

0.68

0.67

0.67

0.76

0.75

0.75

0.81

0.81

0.80

11

12

0.44

0.43

0.49

0.48

0.54

0.53

0.66

0.66

0.74

0.74

0.80

0.80

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TABLE 25(2)


CABLE TYPE: MULTICORE

INSTALLATION

CONDITIONS:


1 2 3 4 5 6

Number of

cables in group

Derating factors

Touching

Distance (S), m

0.15 0.30 0.45 0.60

2

3

4

0.81

0.70

0.63

0.87

0.78

0.74

0.91

0.84

0.81

0.93

0.88

0.86

0.95

0.90

0.89

5

6

7

0.59

0.55

0.52

0.70

0.68

0.66

0.78

0.77

0.75

0.84

0.83

0.82

0.87

0.87

0.86

8

9

10

0.50

0.48

0.47

0.64

0.63

0.62

0.75

0.74

0.73

0.81

0.81

0.80

0.86

0.85

0.85

11

12

0.45

0.44

0.61

0.60

0.73

0.72

0.80

0.80

0.85

0.84

NOTES:

1 For derating factors applicable to other arrangements of single-core and multicore cables laid direct in the

ground, refer to ERA Report 69-30 or alternative specifications.

2 The derating factors have been determined from the hottest cable in the group and assume that all cables

are of the same thermal grade of insulation.

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TABLE 26(1)



INSTALLATION

CONDITIONS:

IN UNDERGROUND WIRING ENCLOSURES—ENCLOSED

SEPARATELY

1 2 3 4

Number of

circuits

Derating factor


0.45 0.60

2

3

4

0.87

0.78

0.74

0.91

0.84

0.81

0.93

0.87

0.85

5

6

7

0.70

0.69

0.67

0.79

0.78

0.76

0.83

0.82

0.82

8

9

10

0.66

0.65

0.64

0.76

0.75

0.75

0.81

0.81

0.80

11

12

0.63

0.63

0.74

0.74

0.80

0.80

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TABLE 26(2)


CABLE TYPES: SINGLE-CORE OR MULTICORE

INSTALLATION

CONDITIONS:

IN UNDERGROUND WIRING ENCLOSURES—MULTICORE CABLES

ENCLOSED SEPARATELY OR MORE THAN ONE SINGLE-CORE

CABLE PER WIRING ENCLOSURE

1 2 3 4 5

Number of

circuits

Derating factor


0.30 0.45 0.60

2

3

4

0.90

0.83

0.79

0.93

0.88

0.85

0.95

0.91

0.89

0.96

0.93

0.92

5

6

7

0.75

0.73

0.71

0.83

0.82

0.81

0.88

0.87

0.86

0.91

0.90

0.89

8

9

10

0.70

0.68

0.67

0.80

0.79

0.79

0.85

0.85

0.85

0.89

0.89

0.89

11

12

0.66

0.66

0.78

0.78

0.84

0.84

0.88

0.88

NOTE: For derating factors applicable to other arrangements of cables in underground wiring

enclosures, refer to ERA Report 69-30 or alternative specifications.

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TABLE 27(1)

RATING FACTORS

VARIANCE: AIR AND CONCRETE SLAB AMBIENT TEMPERATURES

INSTALLATION

CONDITIONS:

CABLES IN AIR OR HEATED CONCRETE SLABS

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

Conductor

tempera-

ture

°C

Rating factor

Air and concrete slab ambient temperature (See Notes 1, 2 & 3), °C

15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 100 110 120 130 140

150

110

90

1.11

1.16

1.26

1.09

1.13

1.20

1.07

1.10

1.15

1.04

1.07

1.10

1.02

1.04

1.05

1.0

1.0

1.0

0.98

0.96

0.94

0.95

0.93

0.88

0.93

0.89

0.81

0.90

0.85

0.73

0.88

0.80

0.65

0.85

0.76

0.57

0.83

0.71

0.47

0.80

0.65

0.34

0.77

0.60

0.19

0.74

0.53

—

0.69

0.38

—

0.60

—

—

0.52

—

—

0.43

—

—

0.30

—

—

80

75

1.31

1.35

1.25

1.28

1.19

1.21

1.12

1.14

1.06

1.07

1.0

1.0

0.92

0.91

0.84

0.82

0.76

0.72

0.66

0.60

0.56

0.49

0.45

0.37

0.27

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

NOTES:

1 For heated concrete slabs, the ambient temperature shall be taken as the operating temperature of the slab.

2 The normal usage of high temperature insulation cables is in ambient air temperatures greater than 40°C,

see Table 17.

3 For cables with a maximum permissible operating temperature above the normal use temperatures

specified in Table 3, derating may not be necessary (see Notes to Table 1 for further details)

TABLE 27(2)

RATING FACTORS

VARIANCE: SOIL AMBIENT TEMPERATURE

INSTALLATION

CONDITIONS:

CABLES BURIED DIRECT IN GROUND OR IN UNDERGROUND

WIRING ENCLOSURES

1 2 3 4 5 6 7 8

Conductor

temperature

°C

Rating factor

Soil ambient temperature, °C

10 15 20 25 30 35 40

110

90

80

1.08

1.11

1.13

1.06

1.07

1.09

1.03

1.03

1.04

1.0

1.0

1.0

0.97

0.97

0.96

0.94

0.93

0.91

0.91

0.89

0.85

75 1.14 1.10 1.05 1.0 0.95 0.89 0.83

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TABLE 28(1)

RATING FACTORS


VARIANCE: DEPTH OF LAYING

INSTALLATION

CONDITIONS:


1 2 3 4

Depth of laying

m

Rating factor

Conductor size, mm2

Up to 50 Above 50 up to 300 Above 300

0.5

0.6

0.8

1.00

0.99

0.97

1.00

0.98

0.96

1.00

0.97

0.94

1.0

1.25

1.5

0.95

0.94

0.93

0.94

0.92

0.91

0.92

0.90

0.89

1.75

2.0

2.5

0.92

0.91

0.90

0.89

0.88

0.87

0.87

0.86

0.85

3.0 or more 0.89 0.86 0.83

NOTE: The ambient temperature at the surface is to be taken at 40°C and not 25°C as at a

depth of 0.5 m.

TABLE 28(2)

RATING FACTORS


VARIANCE: DEPTH OF LAYING

INSTALLATION

CONDITIONS:

IN UNDERGROUND WIRING ENCLOSURES

1 2 3

Depth of laying

m

Rating factor

Single-core* Multicore

0.5

0.6

0.8

1.00

0.98

0.95

1.00

0.99

0.97

1.0

1.25

1.5

0.93

0.90

0.89

0.96

0.95

0.94

1.75

2.0

2.5

0.88

0.87

0.86

0.94

0.93

0.93

3.0 or more 0.85 0.92

* These rating factors apply to single-core cables enclosed separately, or grouped in a single wiring

enclosure.

NOTE: The ambient temperature at the surface is to be taken as 40°C and not 25°C as at a

depth of 0.5 m. For depth less than 0.5 m, see Table 3(4).

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TABLE 29

RATING FACTORS

VARIANCE: THERMAL RESISTIVITY OF THE SOIL (FROM 1.2°C.m/W)

INSTALLATION

CONDITIONS:

BURIED DIRECT IN GROUND AND IN UNDERGROUND WIRING

ENCLOSURES

1 2 3 4 5 6

Rating factor

Thermal

resistivity of soil

°C.m/W

Multicore cable

buried direct

Two or three

single-core

cables buried

direct

Multicore cable

in a wiring

enclosure

Two single- core

cables in a

wiring

enclosure*

Three single-

core cables in a

wiring

enclosure*

0.8

0.9

1.0

1.09

1.07

1.04

1.16

1.11

1.07

1.03

1.02

1.02

1.06

1.04

1.03

1.08

1.06

1.04

1.2

1.5

2.0

1.00

0.92

0.81

1.00

0.90

0.80

1.00

0.95

0.88

1.00

0.94

0.86

1.00

0.92

0.83

2.5

3.0

0.74

0.69

0.72

0.66

0.83

0.78

0.80

0.75

0.77

0.71

* These rating factors apply to single-core cables enclosed separately, or grouped in a single wiring enclosure.

NOTE: See Clause 3.5.5 for additional information on thermal resistivity of soil.

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S E C T I O N 4 V O L T A G E D R O P

4.1 GENERAL

The provisions of this Section apply to the selection of conductor sizes with regard to voltage drop.

NOTE: AS/NZS 3000 imposes limitations on circuit arrangements in order to restrict excessive

voltage drop between supply and load.

Clauses 4.2 and 4.3 describe a simplified method of determining the voltage drop for use with Tables 40 to 50 for applications where only the route length and load current of balanced circuits are known.

Clauses 4.4 and 4.5 describe a more accurate method of determining the voltage drop for use with Tables 30 to 39 where the cable size is known or anticipated.

Clause 4.6 describes a method for determining the voltage drop where unbalanced load current conditions occur.

4.2 DETERMINATION OF VOLTAGE DROP FROM MILLIVOLTS PER AMPERE

METRE

The voltage drop (mV/A.m) values given in Tables 40 to 50 are for various cable types and configurations and maximum operating temperatures.

In applying these voltage drop values, the smallest permissible conductor is the smallest that satisfies the following equations:

IL

VV

×= d

c

1000 . . . 4.2(1)

1000

c

d

VILV

××= . . . 4.2(2)

Vp ≥ sum of Vd on circuit run

where

Vc = the millivolt drop per ampere-metre route length of circuit, as shown in the tables for various conductors, in millivolts per ampere metre (mV/A.m)

NOTES:

1 To convert single-phase voltage drop (mV/A.m) values to three-phase values, multiply the

single-phase values by 0.866 ⎟⎟

⎠

⎞

⎜⎜

⎝

⎛

2

3. To convert three-phase values to single-phase

values, multiply the three-phase values by 1.155 ⎟⎟⎠

⎞⎜⎜⎝

⎛

3

2.

2 Paragraph C4 and C7 of AS/NZS 3000:2007 details a simplified method of calculating the

voltage drop for PVC cables up to 95 mm2, operating at 75°C with maximum values of Vc.

The method allows the addition of single phase and three phase percentages.

Vd = actual voltage drop, in volts

Vp = permissible voltage drop on the circuit run, e.g. 5% of supply voltage, in volts

L = route length of circuit, in metres

I = the current to be carried by the cable, in amperes.

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The voltage drop values in Tables 40 to 50 may not be applicable under the following conditions:

(a) Where the cable operating temperature is lower than the maximum temperature permitted for the insulation material. See Clause 4.4 for a method of determining the cable operating temperature for use with the tables.

(b) Where the load power factor and cable power factor do not give rise to conditions for maximum voltage drop, or the load power factor for larger size conductors varies from 0.8 lagging. See Clause 4.5 for a method of determining the voltage drop where other power factor values are known to be consistent.

(c) Where out-of-balance load conditions exist. See Clause 4.6 for a method of determining the actual voltage drop on a circuit where out-of-balance loads are known to be consistent.

4.3 DETERMINATION OF VOLTAGE DROP FROM CIRCUIT IMPEDANCE

4.3.1 General

Voltage drop in a circuit represents the vectorial difference in voltage between the origin or supply end and the load end. For the purpose of determining the maximum voltage drop value in Clause 4.2, the voltage drop (Vd) has been related to the impedance of the cables forming the circuit when the power factor of the cable is equal to the power factor of the load, in which case—

Vd = IZc . . . 4.3(1)

where

Vd = voltage drop in cable, in volts

I = current flowing in cable, in amperes

Zc = impedance of cable, in ohms

= √(R2c + X2

c)

where

Rc = cable resistance, in ohms; a function of the material, size and temperature of the conductors

Xc = cable reactance, in ohms; a function of the conductor shape and cable spacing

= 0, for direct current conditions.

The reactance Xc and resistance Rc of cables is expressed in this Standard as ohms per kilometre, which enables the total impedance Zc for any given cable route length L to be readily calculated.

Therefore the maximum volt drop in a cable, when the power factor of the cable is equal to the power factor of the load is obtained by multiplying the cable impedance Zc by the length of cable and the current as follows:

1000

c

d

ILZV = . . . 4.3(2)

where

L = route length, in metres (see Clause 1.5.6)

Vd = voltage drop in cable, in volts

Zc = impedance of cable, in ohms/km Acc

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4.3.2 Single-phase, two-wire supply system

For a single-phase circuit the impedance of the active and neutral conductors is taken into account. As these conductors are of the same material and generally the same size, the voltage drop on the circuit is twice what it would be for a single cable—

1000

cdIφ

ILZV = or

1000

) 2cZ ( L I

. . . 4.3(3)

4.3.3 Three-phase, three-wire or four-wire supply system

For a balanced three-phase circuit no current is flowing in the neutral conductor and at any given instant the current flowing in one active conductor will be balanced by the currents flowing in the other active conductors. The voltage drop per phase to neutral is the voltage drop in one cable and the voltage drop between phases is therefore—

1000

3 =

c

3 d

ILZV

√φ or

1000

) c

Z3 ( L I √ . . . 4.3(4)

As the single-phase voltage drop (mV/A.m) values represent 2Zc and the three-phase voltage drop (mV/A.m) values represent √3Zc, then the following conversions may be used:

(a) Single-phase voltage drop (mV/A.m) value = 1.155 × three-phase voltage drop (mV/A.m) value.

(b) Three-phase voltage drop (mV/A.m) value = 0.866 × single-phase voltage drop (mV/A.m) value.

4.3.4 Two-phase, three-wire, earthed neutral 120-degree supply system

For a balanced two-phase circuit of this type the current flowing in the neutral conductor will balance the currents flowing in the active conductors. The voltage drop may be assessed on a single-phase basis by summing the voltage drop in one active conductor (IZc) with the in-phase component of voltage drop in the neutral (0.5IZc), i.e.

1000

0.5 + =

ccd

ILZILZV

=1000

) 51c

ILZ ( .

= V . φ 1 d750

. . . 4.3(5)

4.3.5 Single-phase, three-wire, earthed centre-tapped 180-degree supply system

For a balanced single-phase circuit of this type no current is flowing in the neutral or centre-tapped conductor. Therefore the voltage drop on a single-phase basis will only be that associated with the current flowing in one active conductor, i.e.

1000 =

cd

ILZV . . . 4.3(6)

= φ1d5.0 V

4.4 DETERMINATION OF VOLTAGE DROP FROM CABLE OPERATING

TEMPERATURE

As described in Clause 3.2.2 and Table 1 of this Standard, the sustained cable current-carrying capacities given in Tables 4 to 19 are based on cables operating at the maximum conductor temperature permitted by the cable insulation material when installed in specified ambient conditions. In many situations, however, the cable operating temperature is considerably less than the maximum figure. Some situations where this will occur are as follows:

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(a) Cables sizes are selected in order not to exceed a certain voltage drop figure.

(b) Cable sizes are selected for convenience, mechanical strength or short-circuit capacity as required by AS/NZS 3000.

(c) The ambient air or soil temperatures are consistently below the specified or standard conditions.

The conductor temperature can be estimated using the following equation:

AR

A0

2

0

θ−θθ−θ=⎟⎟

⎠

⎞⎜⎜⎝

⎛

RI

I . . . 4.4(1)

where

I0 = operating current, in amperes

IR = rated current given in Tables 4 to 21, in amperes

(For cable affected by the presence of certain external influences as detailed inClauses 3.5.2 to 3.5.8, it will be necessary to correct the rated current given in Tables 4 to 21 by the application of an appropriate rating factor or factorsobtained from Tables 22 to 29.)

θ0 = operating temperature of cable when carrying I0, in degrees Celsius

θR = operating temperature of the cable when carrying IR, in degrees Celsius

θA = ambient air or soil temperature, in degrees Celsius

The calculated operating temperature (θ0) is then raised to the nearest temperature 45°C, 60°C, 75°C, 80°C, 90°C or 110°C for use with Tables 34 to 50 to determine the cable a.c. resistance and three-phase voltage drop.

4.5 DETERMINATION OF VOLTAGE DROP FROM LOAD POWER FACTOR

The relationship between the supply and load voltages under different conditions of load power factor is illustrated in the phasor diagrams of Figure 2.

From the phasor diagrams of Figure 2 it can be seen that a larger value of supply voltage is required to maintain a given load voltage when the current is lagging the voltage than when the same current and voltage are in phase. Furthermore, a still smaller supply voltage is required to maintain the given load voltage when the current leads the load voltage.

The voltage drop (IZc) is the same in all cases, but because of the different power factors the voltage (IZc) is added to the load voltage at a different angle in each case. It can be seen that in the particular instance where the cable power factor and the load power factor are equal, the voltage drop (Vd) is a maximum of IZc as discussed in Clause 4.3.

In other situations of load power factor the difference between the magnitudes of the supply voltage (E) and the load voltage (VL) is smaller. It will be noted that the magnitude of the phasors IRc and IXc has been exaggerated with respect to VL in Figure 2 to illustrate the point. In practice the voltage drop is very much smaller than the supply voltage and the difference between the magnitudes of the supply and load voltages may be approximated by the following equation:

E − VL = I(Rc cos θ + Xc sin θ) for lagging p.f. . . . 4.5(1)

= I(Rc cos θ − Xc sin θ) for leading p.f. . . . 4.5(2)

Therefore for a single-phase system:

Vd1φ = IL [2(Rc cos θ + Xc sin θ)] . . . 4.5(3)

and a three-phase system:

A1

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Vd3φ = IL [√3(Rc cos θ + Xc sin θ)] . . . 4.5(4)

where

L = route length of circuit, in metres

Rc = cable resistance, in ohms per metre

Xc = cable reactance, in ohms per metre.

Values of Rc and Xc are given in units of ohms per kilometre (Ω/km) in Tables 30 to 39. It will be noted that the influence of skin effect on resistance has been taken into account in the specification of cable resistance values in Tables 38 to 43 and as such are referred to as values of a.c. resistance.

FIGURE 2 PHASOR DIAGRAMS ILLUSTRATING VOLTAGE DROP

VARIATION WITH LOAD POWER FACTOR

4.6 DETERMINATION OF VOLTAGE DROP IN UNBALANCED MULTIPHASE

CIRCUITS

For unbalanced multiphase circuits, current will be flowing in the neutral conductor as illustrated in the phasor diagram of Figure 3.

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FIGURE 3 PHASOR DIAGRAM OF CURRENTS IN

UNBALANCED THREE-PHASE CIRCUIT

A conservative solution to the voltage drop assessment in these situations would be to assume balanced three-phase load conditions and perform calculations using the current flowing in the heaviest-loaded phase. In many cases this will still be necessary if the out-of-balance conditions are inconsistent or intermittent.

However, where the currents in each phase can be shown to be of different magnitudes for consistent periods, voltage drop calculations can be performed on a single-phase basis by geometrically summing the voltage drop in the heaviest loaded phase and the voltage drop in the neutral, as follows:

Vd = voltage drop in heaviest loaded active + voltage drop in neutral

= IALAZcA + INLNZcN . . . 4.6(1)

The voltage drop in each conductor can then be assessed with a knowledge of the specific conductor material, size, temperature and length, the magnitude and phase angle of the current flowing in each conductor, and the phase angle of the load by using the appropriate equations given in this Clause.

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TABLE 30

REACTANCE (Xc) AT 50 Hz

CABLE TYPE: ALL CABLES EXCLUDING FLEXIBLE CORDS, FLEXIBLE CABLES,

MIMS CABLES AND AERIAL CABLES

1 2 3 4 5 6 7 8 9 10 11 12

Conductor

size

Reactance (Xc) at 50 Hz, Ω/km

Single-core Multicore

Trefoil (or single phase) Flat touching* Circular conductors Shaped conductors

mm2 Elastomer PVC XLPE Elastomer PVC XLPE Elastomer PVC XLPE PVC XLPE

1

1.5

2.5

0.179

0.167

0.153

0.168

0.157

0.143

0.166

0.155

0.141

0.194

0.183

0.168

0.184

0.172

0.159

0.181

0.170

0.156

0.139

0.129

0.118

0.119

0.111

0.102

0.114

0.107

0.0988

—

—

—

—

—

—

4

6

10

0.142

0.133

0.123

0.137

0.128

0.118

0.131

0.123

0.114

0.157

0.148

0.138

0.152

0.143

0.134

0.146

0.138

0.129

0.110

0.104

0.0967

0.102

0.0967

0.0906

0.0930

0.0887

0.0840

—

—

—

—

—

—

16

25

35

0.114

0.109

0.104

0.111

0.106

0.101

0.106

0.102

0.0982

0.130

0.125

0.120

0.126

0.121

0.117

0.122

0.118

0.113

0.0913

0.0895

0.0863

0.0861

0.0853

0.0826

0.0805

0.0808

0.0786

0.0794

0.0786

0.0761

0.0742

0.0744

0.0725

50

70

95

0.0988

0.0941

0.0924

0.0962

0.0917

0.0904

0.0924

0.0893

0.0868

0.114

0.109

0.108

0.111

0.107

0.106

0.108

0.104

0.102

0.0829

0.0798

0.0790

0.0797

0.0770

0.0766

0.0751

0.0741

0.0725

0.0734

0.0710

0.0706

0.0692

0.0683

0.0668

120

150

185

0.0889

0.0885

0.0878

0.0870

0.0868

0.0862

0.0844

0.0844

0.0835

0.104

0.104

0.103

0.102

0.102

0.101

0.0996

0.0996

0.0988

0.0765

0.0765

0.0762

0.0743

0.0745

0.0744

0.0713

0.0718

0.0720

0.0685

0.0687

0.0686

0.0657

0.0662

0.0663

240

300

400

0.0861

0.0852

0.0841

0.0847

0.0839

0.0829

0.0818

0.0809

0.0802

0.101

0.100

0.0993

0.0999

0.0991

0.0982

0.0970

0.0961

0.0955

0.0751

0.0746

0.0740

0.0735

0.0732

0.0728

0.0709

0.0704

0.0702

0.0678

0.0675

0.0671

0.0653

0.0649

0.0647

500

630

0.0830

0.0809

0.0820

0.0800

0.0796

0.0787

0.0983

0.0961

0.0973

0.0952

0.0948

0.0940

0.0734

—

0.0723

—

0.0700

—

0.0666

—

0.0645

—

* These reactance values may also be used as a conservative estimate for cables that are not strictly arranged ‘flat

touching’, e.g. where cables are installed in a wiring enclosure.

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TABLE 31


CABLE TYPES: FLEXIBLE CORDS AND FLEXIBLE CABLES

1 2 3 4 5 6 7 8 9 10

Conductor

size



Trefoil (or single phase) Flat touching* Circular conductors

mm2 Elastomer PVC XLPE Elastomer PVC XLPE Elastomer PVC XLPE

0.5

0.75

1

0.192

0.179

0.171

0.180

0.168

0.161

0.178

0.166

0.158

0.207

0.194

0.186

0.195

0.183

0.176

0.193

0.181

0.173

0.153

0.142

0.136

0.131

0.122

0.116

0.125

0.117

0.111

1.5

2.5

4

0.160

0.149

0.137

0.150

0.139

0.132

0.148

0.137

0.126

0.176

0.164

0.152

0.165

0.155

0.147

0.163

0.153

0.141

0.127

0.118

0.108

0.109

0.101

0.100

0.105

0.0977

0.0911 6

10

16

0.129

0.116

0.109

0.124

0.112

0.105

0.119

0.107

0.101

0.144

0.131

0.124

0.139

0.127

0.120

0.134

0.123

0.116

0.103

0.0936

0.0887

0.0954

0.0876

0.0835

0.0871

0.0810

0.0779 25

35

50

0.104

0.0991

0.0964

0.1010

0.0961

0.0938

0.0973

0.0930

0.0901

0.119

0.114

0.112

0.116

0.111

0.109

0.113

0.108

0.105

0.0871

0.0839

0.0832

0.0829

0.0801

0.0799

0.0783

0.0761

0.0754 70

95

120

0.0917

0.0905

0.0872

0.0894

0.0885

0.0854

0.0869

0.0849

0.0828

0.107

0.106

0.102

0.105

0.104

0.101

0.102

0.100

0.0980

0.0800

0.0796

0.0774

0.0773

0.0771

0.0753

0.0744

0.0729

0.0723 150

185

240

0.0870

0.0862

0.0849

0.0853

0.0847

0.0835

0.0830

0.0821

0.0808

0.102

0.101

0.100

0.101

0.0999

0.0988

0.0982

0.0973

0.0960

0.0775

0.0771

0.0764

0.0755

0.0754

0.0749

0.0728

0.0730

0.0722 300

400

500

0.0842

0.0825

0.0812

0.0830

0.0814

0.0803

0.0800

0.0788

0.0780

0.0994

0.0977

0.0965

0.0982

0.0966

0.0955

0.0953

0.0941

0.0932

0.0761

0.0750

0.0743

0.0747

0.0738

0.0732

0.0718

0.0714

0.0711 630 0.0797 0.0789 0.0777 0.0950 0.0941 0.0929 — — —

* These reactance values may also be used as a conservative estimate for cables that are not strictly arranged ‘flat

touching’, e.g. where cables are installed in a wiring enclosure.

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TABLE 32


CABLE TYPE: MIMS

Conductor

size

mm2


Single-core

(trefoil

formation)

Multicore

0.6/0.6 kV cables

1

1.5

2.5

4

0.123

0.116

0.107

0.101

0.0912

0.0865

0.0814

—

1/1 kV cables

1.5

2.5

4

0.139

0.128

0.120

0.1010

0.0937

0.0879

6

10

16

0.112

0.104

0.0976

0.0835

0.0788

0.0752

25

35

50

0.0927

0.0889

0.0854

0.0723

—

—

70

95

120

0.0827

0.0804

0.0785

—

—

—

150

185

240

0.0772

0.0784

0.0768

—

—

—

300

400

0.0777

0.0784

—

—

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TABLE 33


CABLE TYPE: SINGLE-CORE AERIAL WITH BARE OR INSULATED CONDUCTORS

Conductor size

(mm2)

or

stranding (No./mm)

Reactance (Xc) of 50 Hz, Ω/km*

Single phase and

trefoil

Three cores in flat

formation

7/1.00

6

7/1.25

0.371

0.368

0.357

0.385

0.383

0.371

10

16

7/1.75

0.352

0.337

0.336

0.366

0.352

0.350

7/2.00

25

35

0.327

0.317

0.309

0.342

0.332

0.324

7/2.50

7/2.75

50

0.313

0.307

0.300

0.328

0.322

0.314

19/1.75

7/3.00

19/2.00

0.301

0.302

0.292

0.315

0.316

0.307

70

7/3.50

7/3.75

0.288

0.292

0.288

0.303

0.307

0.302

95

37/1.75

7/4.50

0.278

0.279

0.276

0.292

0.293

0.291

19/2.75

120

7/4.75

0.272

0.270

0.273

0.287

0.284

0.287

19/3.00

150

19/3.25

0.267

0.263

0.262

0.282

0.278

0.276

185

19/3.50

37/2.50

0.256

0.257

0.257

0.271

0.272

0.271

* Values are based on a spacing of 0.4 m.

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TABLE 34

a.c. RESISTANCE (Rc) AT 50 Hz


1 2 3 4 5 6 7 8 9 10

Conductor

size

a.c. resistance (Rc) at 50 Hz, Ω/km

Copper* Aluminium

Conductor temperature, °C Conductor temperature, °C

mm2 45 60 75 90 110 45 60 75 90

1

1.5

2.5

23.3

14.9

8.14

24.5

15.7

8.57

25.8

16.5

9.01

27.0

17.3

9.45

28.7

18.4

10.0

—

—

—

—

—

—

—

—

—

—

—

—

4

6

10

5.06

3.38

2.01

5.33

3.56

2.12

5.61

3.75

2.23

5.88

3.93

2.33

6.24

4.17

2.48

—

—

—

—

—

—

—

—

—

—

—

— 16

25

35

1.26

0.799

0.576

1.33

0.842

0.607

1.40

0.884

0.638

1.47

0.927

0.668

1.56

0.984

0.710

2.10

1.32

0.956

2.22

1.39

1.01

2.33

1.47

1.06

2.45

1.54

1.11 50

70

95

0.426

0.295

0.213

0.448

0.311

0.225

0.471

0.327

0.236

0.494

0.342

0.247

0.524

0.363

0.262

0.706

0.488

0.353

0.745

0.515

0.372

0.783

0.542

0.392

0.822

0.568

0.411 120

150

185

0.170

0.138

0.111

0.179

0.145

0.117

0.188

0.153

0.123

0.197

0.160

0.129

0.208

0.169

0.136

0.279

0.228

0.182

0.295

0.240

0.192

0.310

0.253

0.202

0.325

0.265

0.212 240

300

400

0.0862

0.0703

0.0569

0.0905

0.0736

0.0595

0.0948

0.0770

0.0620

0.0991

0.0803

0.0646

0.105

0.0846

0.0677

0.140

0.113

0.0890

0.147

0.119

0.0936

0.155

0.125

0.0981

0.162

0.130

0.103 500

630

0.0467

0.0389 0.0487

0.0404 0.0506

0.0418 0.0525

0.0432 0.0547

0.0448

0.0709

0.0571 0.0744

0.0597 0.0779

0.0623 0.0813

0.0649

* For the a.c. resistance of tinned copper conductor, multiply copper value by 1.01.

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TABLE 35


CABLE TYPE: MULTICORE WITH CIRCULAR CONDUCTORS

1 2 3 4 5 6 7 8 9 10

Conductor

size


Copper* Aluminium


mm2 45 60 75 90 110 45 60 75 90

1

1.5

2.5

23.3

14.9

8.14

24.5

15.7

8.57

25.8

16.5

9.01

27.0

17.3

9.45

28.7

18.4

10.0

—

—

—

—

—

—

—

—

—

—

—

—

4

6

10

5.06

3.38

2.01

5.33

3.56

2.12

5.61

3.75

2.23

5.88

3.93

2.33

6.24

4.17

2.48

—

—

—

—

—

—

—

—

—

—

—

—

16

25

35

1.26

0.799

0.576

1.33

0.842

0.607

1.40

0.884

0.638

1.47

0.927

0.669

1.56

0.984

0.710

2.10

1.32

0.956

2.22

1.39

1.01

2.33

1.47

1.06

2.45

1.54

1.11

50

70

95

0.426

0.295

0.214

0.449

0.311

0.225

0.471

0.327

0.236

0.494

0.343

0.248

0.524

0.364

0.262

0.706

0.488

0.353

0.745

0.515

0.373

0.784

0.542

0.392

0.822

0.569

0.411

120

150

185

0.170

0.139

0.112

0.179

0.146

0.118

0.188

0.153

0.123

0.197

0.160

0.129

0.209

0.170

0.136

0.280

0.228

0.182

0.295

0.241

0.192

0.310

0.253

0.202

0.325

0.265

0.212

240

300

400

0.0870

0.0712

0.0580

0.0912

0.0745

0.0605

0.0955

0.0778

0.0630

0.0998

0.0812

0.0656

0.105

0.0852

0.0685

0.140

0.113

0.0897

0.148

0.119

0.0943

0.155

0.125

0.0988

0.162

0.131

0.103

500 0.0486 0.0506 0.0525 0.0544 0.0565 0.0730 0.0765 0.0800 0.0835


TABLE 36


CABLE TYPE: MULTICORE WITH SHAPED CONDUCTORS

1 2 3 4 5 6 7 8 9

Conductor

size


Copper* Aluminium


mm2 45 60 75 90 45 60 75 90

16

25

35

1.26

0.799

0.576

1.33

0.842

0.607

1.40

0.884

0.638

1.47

0.927

0.669

2.10

1.32

0.956

2.22

1.39

1.01

2.33

1.47

1.06

2.45

1.54

1.11

50

70

95

0.426

0.295

0.213

0.448

0.311

0.224

0.471

0.327

0.236

0.494

0.342

0.247

0.706

0.488

0.353

0.745

0.515

0.372

0.783

0.542

0.392

0.822

0.568

0.411

120

150

185

0.170

0.138

0.111

0.179

0.145

0.117

0.187

0.153

0.123

0.196

0.160

0.128

0.279

0.228

0.182

0.295

0.240

0.192

0.310

0.253

0.202

0.325

0.265

0.211

240

300

400

0.0859

0.0698

0.0563

0.0902

0.0732

0.0589

0.0945

0.0766

0.0615

0.0988

0.0800

0.0641

0.139

0.112

0.0886

0.147

0.118

0.0932

0.154

0.124

0.0978

0.162

0.130

0.102

500 0.0466 0.0486 0.0506 0.0526 0.0716 0.0752 0.0788 0.0824


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TABLE 37


CABLE TYPES: FLEXIBLE CORDS AND FLEXIBLE CABLES WITH COPPER

CONDUCTORS*

1 2 3 4 5 6 7 8 9 10 11

Conductor

size




mm2 45 60 75 90 110 45 60 75 90 110

0.5

0.75

1

42.8

28.6

21.4

45.1

30.1

22.6

47.4

31.6

23.7

49.7

33.2

24.9

52.8

35.2

26.4

42.8

28.6

21.4

45.1

30.1

22.6

47.4

31.6

23.7

49.7

33.2

24.9

52.8

35.2

26.4

1.5

2.5

4

14.6

8.76

5.44

15.4

9.23

5.73

16.2

9.70

6.02

17.0

10.2

6.31

18.0

10.8

6.70

14.6

8.76

5.44

15.4

9.23

5.73

16.2

9.70

6.02

17.0

10.2

6.31

18.0

10.8

6.70 6

10

16

3.62

2.10

1.33

3.82

2.21

1.40

4.01

2.32

1.47

4.21

2.44

1.54

4.47

2.59

1.64

3.62

2.10

1.33

3.82

2.21

1.40

4.01

2.32

1.47

4.21

2.44

1.54

4.47

2.59

1.64 25

35

50

0.857

0.609

0.424

0.903

0.641

0.447

0.949

0.674

0.470

0.995

0.707

0.493

1.06

0.750

0.523

0.857

0.609

0.425

0.903

0.642

0.447

0.949

0.674

0.470

0.995

0.707

0.493

1.06

0.750

0.523 70

95

120

0.300

0.227

0.178

0.316

0.240

0.188

0.332

0.252

0.197

0.348

0.264

0.207

0.369

0.280

0.219

0.300

0.228

0.179

0.316

0.240

0.188

0.332

0.252

0.198

0.348

0.264

0.207

0.369

0.280

0.219 150

185

240

0.144

0.119

0.0912

0.151

0.125

0.0958

0.159

0.131

0.100

0.166

0.137

0.105

0.176

0.145

0.111

0.144

0.119

0.0920

0.152

0.126

0.0965

0.159

0.132

0.101

0.167

0.138

0.106

0.176

0.146

0.111 300

400

500

0.0745

0.0587

0.0487

0.0780

0.0613

0.0507

0.0817

0.0640

0.0527

0.0853

0.0666

0.0548

0.0898

0.0699

0.0571

0.0753

0.0597

0.0498

0.0789

0.0623

0.0518

0.0825

0.0649

0.0538

0.0860

0.0675

0.0558

0.0905

0.0706

0.0580

* For the a.c. resistance of tinned copper conductors, multiply copper value by 1.01.

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TABLE 38


CABLE TYPE: MIMS

1 2 3 4 5 6 7

Conductor

size


Conductor temperature, °C

mm2 45 60 75 90 100 105

1

1.5

2.5

18.9

12.7

7.61

19.9

13.3

8.02

20.9

14.0

8.43

21.9

14.7

8.83

22.6

15.2

9.11

22.9

15.4

9.24

4

6

10

4.76

3.16

1.89

5.02

3.33

1.99

5.27

3.50

2.09

5.53

3.67

2.20

5.70

3.79

2.26

5.78

3.84

2.30

16

25

35

1.19

0.758

0.541

1.25

0.799

0.570

1.31

0.840

0.599

1.38

0.880

0.628

1.42

0.907

0.647

1.44

0.921

0.657

50

70

95

0.379

0.271

0.201

0.400

0.286

0.211

0.420

0.300

0.222

0.440

0.315

0.233

0.454

0.325

0.240

0.460

0.329

0.243

120

150

185

0.160

0.129

0.105

0.168

0.135

0.110

0.176

0.142

0.116

0.185

0.149

0.121

0.190

0.153

0.125

0.193

0.155

0.127

240

300

400

0.0825

0.0674

0.0527

0.0866

0.0706

0.550

0.0906

0.0739

0.0574

0.0947

0.0771

0.0597

0.0975

0.0792

0.0613

0.0988

0.0803

0.0621

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TABLE 39


CABLE TYPE: SINGLE-CORE AERIAL WITH BARE OR INSULATED CONDUCTORS

1 2 3 4 5 6 7 8 9

Conductor

size (mm2)

or

stranding

(No./mm)

a.c. resistance (Rc) at 50 Hz, Ω/km*

Copper Aluminium


45 60 75 80 45 60 75 80

7/1.00

6

7/1.25

3.57

3.48

2.30

3.76

3.67

2.42

3.95

3.86

2.54

4.02

3.92

2.58

—

—

—

—

—

—

—

—

—

—

—

—

10

16

7/1.75

2.06

1.30

1.16

2.18

1.37

1.23

2.29

1.44

1.29

2.32

1.46

1.31

—

2.10

—

—

2.21

—

—

2.32

—

—

2.36

— 7/2.00

25

35

0.895

0.823

0.593

0.943

0.867

0.625

0.991

0.911

0.657

1.01

0.926

0.667

—

1.32

0.953

—

1.39

1.00

—

1.46

1.06

—

1.48

1.07 7/2.50

7/2.75

50

—

0.476

0.438

—

0.501

0.462

—

0.527

0.485

—

0.535

0.493

0.915

0.757

0.704

0.964

0.797

0.742

1.01

0.838

0.780

1.03

0.852

0.792 19/1.75

7/3.00

19/2.00

0.434

—

0.333

0.457

—

0.351

0.481

—

0.369

0.488

—

0.375

—

0.636

—

—

0.670

—

—

0.704

—

—

0.716

— 70

7/3.50

7/3.75

0.303

0.295

0.256

0.320

0.310

0.270

0.336

0.326

0.284

0.341

0.331

0.288

0.487

—

0.407

0.513

—

0.428

0.539

—

0.450

0.548

—

0.457 95

37/1.75

7/4.50

0.226

0.223

—

0.238

0.235

—

0.250

0.247

—

0.254

0.251

—

0.352

—

0.284

0.371

—

0.299

0.389

—

0.314

0.396

—

0.319 19/2.75

120

7/4.75

0.176

0.174

—

0.186

0.183

—

0.195

0.193

—

0.198

0.196

—

—

0.278

0.255

—

0.293

0.269

—

0.308

0.282

—

0.313

0.287 19/3.00

150

19/3.25

0.148

0.141

—

0.156

0.149

—

0.163

0.156

—

0.166

0.159

—

—

0.227

0.201

—

0.239

0.212

—

0.251

0.223

—

0.255

0.227 185

19/3.50

37/2.50

0.113

—

0.110

0.119

—

0.116

0.125

—

0.122

0.127

—

0.124

0.181

0.173

—

0.190

0.182

—

0.200

0.191

—

0.203

0.194

—

* Values are based on a spacing of 0.4 m.

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TABLE 40

THREE-PHASE VOLTAGE DROP (Vc) AT 50 Hz

CABLE TYPES: SINGLE-CORE INSULATED AND SHEATHED COPPER CONDUCTORS

LAID IN TREFOIL

1 2 3 4 5 6 7 8 9 10 11

Conductor

size

Three-phase voltage drop (Vc) at 50 Hz, mV/A.m


45 60 75 90 110

mm2 Max. 0.8 p.f. Max. 0.8 p.f. Max. 0.8 p.f. Max. 0.8 p.f. Max. 0.8 p.f.

1

1.5

2.5

40.3

25.9

14.1

—

—

—

42.5

27.3

14.9

—

—

—

44.7

28.6

15.6

—

—

—

46.8

30.0

16.4

—

—

—

49.7

31.9

17.4

—

—

—

4

6

10

8.77

5.86

3.49

—

—

—

9.24

6.18

3.67

—

—

—

9.71

6.49

3.86

—

—

—

10.2

6.81

4.05

—

—

—

10.8

7.23

4.30

—

—

—

16

25

35

2.20

1.40

1.01

—

—

—

2.31

1.47

1.07

—

—

—

2.43

1.54

1.12

—

—

—

2.55

1.62

1.17

—

—

—

2.70

1.72

1.24

—

—

—

50

70

95

0.757

0.537

0.402

—

—

—

0.795

0.563

0.420

—

—

—

0.834

0.589

0.439

—

—

—

0.872

0.615

0.457

—

—

—

0.924

0.650

0.481

—

—

—

120

150

185

0.332

0.284

0.245

—

—

0.245

0.345

0.295

0.253

—

—

0.253

0.359

0.305

0.261

—

—

—

0.373

0.316

0.269

—

—

—

0.392

0.331

0.280

—

—

—

240

300

400

0.211

0.191

0.175

0.208

0.185

0.166

0.216

0.195

0.178

0.214

0.190

0.169

0.221

0.198

0.181

0.220

0.195

0.173

0.227

0.202

0.183

0.226

0.199

0.176

0.235

0.208

0.187

0.234

0.206

0.181

500

630

0.165

0.155

0.150

0.138

0.166

0.156

0.153

0.140

0.168

0.157

0.156

0.142

0.170

0.159

0.158

0.144

0.172

0.160

0.162

0.146

NOTE: These Vc values apply to a balanced three-phase circuit in which no current flows in the neutral

conductor. To determine the single phase Vc the current in the neutral conductor needs to be considered by

multiplying the three-phase value by3

2 = 1.155.

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TABLE 41


CABLE TYPES: SINGLE-CORE INSULATED AND SHEATHED COPPER

CONDUCTORS, LAID FLAT TOUCHING OR IN A WIRING

ENCLOSURE

1 2 3 4 5 6 7 8 9 10 11

Conductor

size



45 60 75 90 110


1

1.5

2.5

40.3

25.9

14.1

—

—

—

42.5

27.3

14.9

—

—

—

44.7

28.6

15.6

—

—

—

46.8

30.0

16.4

—

—

—

49.7

31.9

17.4

—

—

—

4

6

10

8.77

5.86

3.49

—

—

—

9.24

6.18

3.68

—

—

—

9.71

6.49

3.86

—

—

—

10.2

6.81

4.05

—

—

—

10.8

7.23

4.30

—

—

—

16

25

35

2.20

1.40

1.02

—

—

—

2.32

1.47

1.07

—

—

—

2.43

1.55

1.12

—

—

—

2.55

1.62

1.18

—

—

—

2.71

1.72

1.25

—

—

—

50

70

95

0.763

0.545

0.413

—

—

—

0.801

0.571

0.431

—

—

—

0.840

0.597

0.449

—

—

—

0.878

0.623

0.467

—

—

—

0.929

0.657

0.491

—

—

—

120

150

185

0.345

0.299

0.262

—

0.299

0.261

0.358

0.309

0.270

—

—

0.269

0.371

0.319

0.277

—

—

0.277

0.385

0.330

0.285

—

—

0.285

0.403

0.344

0.296

—

—

0.296

240

300

400

0.230

0.212

0.198

0.224

0.201

0.181

0.235

0.215

0.200

0.230

0.206

0.185

0.240

0.219

0.202

0.236

0.211

0.189

0.245

0.222

0.205

0.242

0.215

0.192

0.252

0.227

0.208

0.250

0.222

0.197

500

630

0.188

0.179

0.166

0.153

0.190

0.180

0.169

0.155

0.191

0.181

0.172

0.157

0.193

0.182

0.174

0.159

0.195

0.184

0.178

0.162




2 = 1.155.

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TABLE 42


CABLE TYPE: MULTICORE WITH CIRCULAR COPPER CONDUCTORS

1 2 3 4 5 6 7 8 9 10 11

Conductor

size



45 60 75 90 110


1

1.5

2.5

40.3

25.9

14.1

—

—

—

42.5

27.3

14.9

—

—

—

44.7

28.6

15.6

—

—

—

46.8

30.0

16.4

—

—

—

49.7

31.9

17.4

—

—

—

4

6

10

8.77

5.86

3.49

—

—

—

9.24

6.18

3.67

—

—

—

9.71

6.49

3.86

—

—

—

10.2

6.80

4.05

—

—

—

10.8

7.22

4.29

—

—

—

16

25

35

2.19

1.39

1.01

—

—

—

2.31

1.47

1.06

—

—

—

2.43

1.54

1.11

—

—

—

2.55

1.61

1.17

—

—

—

2.70

1.71

1.24

—

—

—

50

70

95

0.751

0.530

0.394

—

—

—

0.790

0.556

0.413

—

—

—

0.829

0.583

0.431

—

—

—

0.868

0.609

0.450

—

—

—

0.920

0.645

0.475

—

—

—

120

150

185

0.323

0.274

0.234

—

—

—

0.337

0.285

0.242

—

—

—

0.351

0.296

0.251

—

—

—

0.366

0.307

0.259

—

—

—

0.385

0.322

0.271

—

—

—

240

300

400

0.198

0.178

0.162

0.198

0.175

0.157

0.204

0.182

0.165

0.204

0.180

0.160

0.210

0.186

0.168

0.210

0.185

0.164

0.216

0.190

0.171

0.216

0.189

0.167

0.224

0.196

0.175

—

0.196

0.172

500 0.152 0.143 0.154 0.146 0.156 0.148 0.158 0.151 0.160 0.155




2 = 1.155.

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TABLE 43


CABLE TYPES: SINGLE-CORE INSULATED AND SHEATHED ALUMINIUM

CONDUCTORS, LAID IN TREFOIL

1 2 3 4 5 6 7 8 9

Conductor

size



45 60 75 90

mm2 Max. 0.8 p.f. Max. 0.8 p.f. Max. 0.8 p.f. Max. 0.8 p.f.

16

25

35

3.65

2.30

1.66

—

—

—

3.85

2.42

1.75

—

—

—

4.05

2.55

1.85

—

—

—

4.25

2.67

1.94

—

—

—

50

70

95

1.23

0.860

0.631

—

—

—

1.30

0.906

0.663

—

—

—

1.37

0.952

0.696

—

—

—

1.43

0.997

0.727

—

—

—

120

150

185

0.507

0.422

0.349

—

—

—

0.532

0.443

0.364

—

—

—

0.558

0.463

0.380

—

—

—

0.582

0.482

0.394

—

—

—

240

300

400

0.283

0.243

0.211

—

—

0.209

0.294

0.251

0.216

—

—

0.216

0.305

0.260

0.222

—

—

0.222

0.314

0.266

0.226

—

—

0.226

500

630

0.188

0.170

0.183

0.162

0.192

0.173

0.188

0.166

0.196

0.175

0.193

0.169

0.197

0.177

0.195

0.172

NOTE: These Vc values apply to a balanced three-phase circuit in which no current flows in

the neutral conductor. To determine the single phase Vc the current in the neutral conductor

needs to be considered by multiplying the three-phase value by 3

2= 1.155.

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TABLE 44


CABLE TYPES: SINGLE-CORE INSULATED AND SHEATHED ALUMINIUM

CONDUCTORS, LAID FLAT TOUCHING

1 2 3 4 5 6 7 8 9

Conductor

size



45 60 75 90

mm2 Max. 0.8 p.f. Max. 0.8 p.f. Max. 0.8 p.f. Max. 0.8 p.f.

16

25

35

3.65

2.30

1.67

—

—

—

3.85

2.42

1.76

—

—

—

4.05

2.55

1.85

—

—

—

4.25

2.67

1.94

—

—

—

50

70

95

1.24

0.866

0.638

—

—

—

1.30

0.911

0.670

—

—

—

1.37

0.956

0.702

—

—

—

1.44

1.00

0.733

—

—

—

120

150

185

0.515

0.432

0.361

—

—

—

0.540

0.452

0.376

—

—

—

0.565

0.472

0.391

—

—

—

0.589

0.491

0.404

—

—

—

240

300

400

0.297

0.260

0.229

—

0.259

0.225

0.308

0.268

0.235

—

0.267

0.231

0.319

0.276

0.240

—

0.275

0.238

0.327

0.281

0.243

—

—

0.242

500

630

0.208

0.192

0.199

0.178

0.212

0.195

0.204

0.181

0.216

0.197

0.209

0.185

0.216

0.198

0.211

0.188




2= 1.155.

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TABLE 45


CABLE TYPE: MULTICORE CABLES WITH CIRCULAR ALUMINIUM CONDUCTORS

1 2 3 4 5 6 7 8 9 10 11

Conductor

size



45 60 75 80 90


16

25

35

3.64

2.29

1.66

—

—

—

3.84

2.42

1.75

—

—

—

4.04

2.54

1.84

—

—

—

4.11

2.59

1.87

—

—

—

4.24

2.67

1.93

—

—

—

50

70

95

1.23

0.856

0.626

—

—

—

1.30

0.902

0.659

—

—

—

1.36

0.948

0.691

—

—

—

1.39

0.966

0.706

—

—

—

1.43

0.993

0.723

—

—

—

120

150

185

0.501

0.416

0.341

—

—

—

0.527

0.436

0.357

—

—

—

0.552

0.457

0.373

—

—

—

0.565

0.468

—

—

—

—

0.577

0.476

0.388

—

—

—

240

300

400

0.274

0.233

0.200

—

—

0.200

0.285

0.242

0.206

—

—

0.206

0.297

0.251

0.212

—

—

—

—

—

—

—

—

—

0.307

0.258

0.216

—

—

—

500 0.178 0.176 0.182 0.181 0.186 0.185 — — 0.189 0.189

NOTES:

1 For aerial bundled cables (ABC) use XLPE single-core, trefoil figures.

2 These Vc values apply to a balanced three-phase circuit in which no current flows in the neutral conductor.

To determine the single phase Vc the current in the neutral conductor needs to be considered by multiplying

the three-phase value by 3

2= 1.155.

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TABLE 46


CABLE TYPES: SINGLE-CORE FLEXIBLE CORDS AND FLEXIBLE CABLES, LAID IN

TREFOIL

1 2 3 4 5 6 7 8 9 10 11

Conductor

size



45 60 75 90 110


0.5

0.75

1

74.2

49.5

37.1

—

—

—

78.2

52.1

39.1

—

—

—

82.2

54.8

41.1

—

—

—

86.1

57.4

43.1

—

—

—

91.4

61.0

45.7

—

—

—

1.5

2.5

4

25.3

15.2

9.42

—

—

—

26.7

16.0

9.92

—

—

—

28.0

16.8

10.4

—

—

—

29.4

17.6

10.9

—

—

—

31.2

18.7

11.6

—

—

—

6

10

16

6.28

3.64

2.31

—

—

—

6.62

3.83

2.43

—

—

—

6.95

4.03

2.56

—

—

—

7.29

4.22

2.68

—

—

—

7.74

4.48

2.84

—

—

—

25

35

50

1.50

1.07

0.754

—

—

—

1.57

1.12

0.792

—

—

—

1.65

1.18

0.831

—

—

—

1.73

1.24

0.869

—

—

—

1.84

1.31

0.921

—

—

—

70

95

120

0.543

0.424

0.344

—

—

—

0.569

0.443

0.358

—

—

—

0.596

0.463

0.373

—

—

—

0.622

0.483

0.388

—

—

—

0.658

0.509

0.408

—

—

—

150

185

240

0.291

0.254

0.215

—

—

0.214

0.302

0.263

0.221

—

—

0.221

0.313

0.272

0.227

—

—

0.227

0.325

0.280

0.233

—

—

0.233

0.340

0.293

0.242

—

—

0.242

300

400

500

0.194

0.175

0.164

0.190

0.166

0.151

0.198

0.178

0.165

0.195

0.170

0.154

0.203

0.180

0.167

0.200

0.174

0.157

0.207

0.183

0.169

0.205

0.178

0.160

0.213

0.187

0.172

0.212

0.183

0.164

630 0.154 0.137 0.155 0.139 0.156 0.141 0.157 0.143 0.159 0.146



multiplying the three-phase value by 3

2= 1.155.

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TABLE 47


CABLE TYPES: SINGLE-CORE FLEXIBLE CORDS AND FLEXIBLE CABLES, LAID

FLAT TOUCHING OR IN A WIRING ENCLOSURE

1 2 3 4 5 6 7 8 9 10 11

Conductor

size



45 60 75 90 110


0.5

0.75

1

74.2

49.5

37.1

—

—

—

78.2

52.1

39.1

—

—

—

82.2

54.8

41.1

—

—

—

86.1

57.4

43.1

—

—

—

91.4

61.0

45.7

—

—

—

1.5

2.5

4

25.3

15.2

9.42

—

—

—

26.7

16.0

9.92

—

—

—

28.0

16.8

10.4

—

—

—

29.4

17.6

10.9

—

—

—

31.2

18.7

11.6

—

—

—

6

10

16

6.28

3.64

2.31

—

—

—

6.62

3.84

2.43

—

—

—

6.96

4.03

2.56

—

—

—

7.29

4.22

2.68

—

—

—

7.74

4.48

2.85

—

—

—

25

35

50

1.50

1.07

0.760

—

—

—

1.58

1.13

0.798

—

—

—

1.66

1.18

0.837

—

—

—

1.74

1.24

0.875

—

—

—

1.84

1.31

0.926

—

—

—

70

95

120

0.551

0.434

0.356

—

—

—

0.577

0.453

0.370

—

—

—

0.603

0.473

0.385

—

—

—

0.630

0.492

0.399

—

—

—

0.665

0.518

0.419

—

—

—

150

185

240

0.305

0.270

0.234

—

0.270

0.230

0.316

0.279

0.240

—

0.278

0.236

0.327

0.287

0.245

—

0.287

0.243

0.338

0.295

0.251

—

—

0.249

0.353

0.307

0.259

—

—

0.258

300

400

500

0.215

0.197

0.187

0.206

0.182

0.167

0.219

0.199

0.188

0.211

0.186

0.170

0.223

0.202

0.190

0.216

0.190

0.173

0.227

0.204

0.192

0.221

0.193

0.176

0.232

0.208

0.194

0.228

0.198

0.179

630 0.178 0.153 0.179 0.155 0.180 0.157 0.181 0.159 0.182 0.162




2= 1.155.

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TABLE 48


CABLE TYPES: MULTICORE FLEXIBLE CORDS AND FLEXIBLE CABLES

1 2 3 4 5 6 7 8 9 10 11

Conductor

size



45 60 75 90 110


0.5

0.75

1

74.2

49.5

37.1

—

—

—

78.2

52.1

39.1

—

—

—

82.2

54.8

41.1

—

—

—

86.1

57.4

43.1

—

—

—

91.4

61.0

45.7

—

—

—

1.5

2.5

4

25.3

15.2

9.42

—

—

—

26.7

16.0

9.92

—

—

—

28.0

16.8

10.4

—

—

—

29.4

17.6

10.9

—

—

—

31.2

18.7

11.6

—

—

—

6

10

16

6.28

3.64

2.31

—

—

—

6.62

3.83

2.43

—

—

—

6.95

4.03

2.55

—

—

—

7.29

4.22

2.68

—

—

—

7.74

4.48

2.84

—

—

—

25

35

50

1.49

1.06

0.749

—

—

—

1.57

1.12

0.788

—

—

—

1.65

1.18

0.827

—

—

—

1.73

1.23

0.866

—

—

—

1.84

1.31

0.917

—

—

—

70

95

120

0.537

0.418

0.337

—

—

—

0.564

0.437

0.352

—

—

—

0.591

0.457

0.367

—

—

—

0.618

0.477

0.383

—

—

—

0.654

0.504

0.403

—

—

—

150

185

240

0.283

0.246

0.207

—

—

0.206

0.295

0.255

0.213

—

—

0.213

0.306

0.264

0.219

—

—

0.219

0.318

0.273

0.225

—

—

—

0.334

0.286

0.234

—

—

—

300

400

500

0.185

0.165

0.154

0.183

0.160

0.145

0.189

0.168

0.156

0.188

0.164

0.148

0.194

0.171

0.158

0.193

0.167

0.151

0.198

0.174

0.160

0.198

0.171

0.154

0.205

0.178

0.163

0.204

0.176

0.158




2= 1.155.

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TABLE 49


CABLE TYPES: SINGLE-CORE AND MULTICORE MIMS, LAID IN TREFOIL

1 2 3 4 5 6 7 8 9 10 11 12 13

Conductor

size



45 60 75 90 100 105

mm2 Max. 0.8 p.f. Max. 0.8 p.f. Max. 0.8 p.f. Max. 0.8 p.f. Max. 0.8 p.f. Max. 0.8 p.f.

0.6/0.6 kV Cables

1

1.5

2.5

32.8

21.9

13.1

—

—

—

34.6

23.0

13.8

—

—

—

36.3

24.2

14.5

—

—

—

38.1

25.4

15.2

—

—

—

39.1

26.3

15.8

31.4

21.2

12.7

39.7

26.7

16.0

31.9

21.5

12.9

4 8.20 — 8.64 — 9.08 — 9.52 — 9.87 8.00 10.01 8.11

1/1 kV Cables

1.5

2.5

4

21.9

13.1

8.20

—

—

—

23.0

13.8

8.64

—

—

—

24.2

14.5

9.08

—

—

—

25.4

15.2

9.52

—

—

—

26.3

15.8

9.87

21.2

12.8

8.02

26.7

16.0

10.01

21.5

12.9

8.13

6

10

16

5.46

3.30

2.06

—

—

—

5.77

3.47

2.17

—

—

—

6.05

3.65

2.28

—

—

—

6.34

3.83

2.39

—

—

—

6.57

3.92

2.47

5.37

3.24

2.07

6.65

3.99

2.50

5.44

3.30

2.10

25

35

50

1.32

0.949

0.672

—

—

—

1.39

0.999

0.706

—

—

—

1.46

1.05

0.741

—

—

—

1.53

1.10

0.775

—

—

—

1.58

1.13

0.800

1.35

0.99

0.718

1.60

1.15

0.810

1.37

1.00

0.726

70

95

120

0.491

0.375

0.307

—

—

—

0.515

0.393

0.320

—

—

—

0.539

0.410

0.333

—

—

—

0.563

0.427

0.346

—

—

—

0.581

0.438

0.356

0.536

0.416

0.345

0.588

0.443

0.361

0.542

0.420

0.349

150

185

240

0.260

0.228

0.195

—

—

0.194

0.270

0.236

0.201

—

—

0.200

0.280

0.243

0.206

—

—

0.206

0.290

0.251

0.211

—

—

0.211

0.297

0.256

0.215

0.292

0.255

0.215

0.300

0.258

0.217

0.295

0.257

0.217

300

400

0.178

0.163

0.173

0.154

0.181

0.166

0.178

0.157

0.185

0.168

0.182

0.161

0.189

0.170

0.187

0.164

0.192

0.172

0.190

0.166

0.194

0.173

0.192

0.168


conductor. To determine the single phase Vc the current in the neutral conductor needs to be considered

by multiplying the three-phase value by 3

2= 1.155.

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TABLE 50


CABLE TYPE: AERIAL WITH BARE OR INSULATED COPPER CONDUCTORS

1 2 3 4 5 6 7 8 9

Conductor

size (mm2)

or

stranding

(No./mm)



45 60 75 80

Max 0.8 p.f Max 0.8 p.f Max 0.8 p.f Max 0.8 p.f

7/1.00

6

7/1.25

6.22

6.06

4.02

—

—

—

6.55

6.39

4.23

—

—

—

6.88

6.71

4.45

—

—

—

6.99

6.82

4.52

—

—

—

10

16

7/1.75

3.63

2.32

2.10

—

—

—

3.82

2.44

2.20

—

—

—

4.01

2.55

2.31

—

—

—

4.07

2.59

2.34

—

—

—

7/2.00

25

35

1.65

1.53

1.16

—

—

—

1.73

1.60

1.21

—

—

—

1.81

1.67

1.26

—

—

—

1.83

1.69

1.27

—

—

—

7/2.75

50

19/1.75

0.981

0.920

0.915

—

—

—

1.02

0.954

0.948

—

—

—

1.06

0.988

0.982

—

—

—

1.07

1.00

0.993

—

—

—

19/2.00

70

7/3.50

0.768

0.725

0.719

0.765

0.720

0.712

0.791

0.745

0.738

0.790

0.742

0.734

0.815

0.767

0.758

0.815

0.765

0.756

0.823

0.774

0.765

0.823

0.772

0.763

7/3.75

95

37/1.75

0.667

0.620

0.619

0.654

0.601

0.599

0.683

0.633

0.632

0.673

0.618

0.616

0.700

0.647

0.646

0.692

0.635

0.632

0.705

0.652

0.650

0.698

0.640

0.638

19/2.75

120

19/3.00

0.562

0.556

0.529

0.527

0.521

0.482

0.571

0.565

0.535

0.540

0.534

0.493

0.580

0.574

0.542

0.553

0.547

0.504

0.584

0.577

0.545

0.558

0.551

0.508

150

185

37/2.50

0.517

0.485

0.484

0.469

0.422

0.419

0.523

0.489

0.488

0.479

0.431

0.427

0.530

0.493

0.492

0.490

0.439

0.435

0.532

0.495

0.493

0.493

0.442

0.438



needs to be considered by multiplying the three-phase value by3

2 = 1.155.

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TABLE 51


CABLE TYPE: AERIAL WITH BARE OR INSULATED ALUMINIUM CONDUCTORS

1 2 3 4 5 6 7 8 9

Conductor

size (mm2)

or

stranding

(No./mm)



45 60 75 80

Max. 0.8 p.f. Max. 0.8 p.f. Max. 0.8 p.f. Max. 0.8 p.f.

16

25

35

3.68

2.35

1.74

—

—

—

3.87

2.47

1.82

—

—

—

4.07

2.59

1.91

—

—

—

4.13

2.63

1.93

—

—

—

7/2.50

7/2.75

50

1.68

1.41

1.33

—

—

—

1.76

1.48

1.39

—

—

—

1.84

1.55

1.45

—

—

—

1.86

1.57

1.47

—

—

—

7/3.00

70

7/3.75

1.22

0.980

0.863

—

—

—

1.27

1.02

0.894

—

—

—

1.33

1.06

0.925

—

—

—

1.35

1.07

0.936

—

—

—

95

7/4.50

120

0.776

0.686

0.671

0.776

0.680

0.666

0.802

0.705

0.690

—

0.701

0.686

0.829

0.725

0.709

—

0.722

0.707

0.837

0.731

0.715

—

0.729

0.714

7/4.75

150

19/3.25

0.647

0.601

0.572

0.637

0.587

0.551

0.664

0.615

0.584

0.656

0.604

0.566

0.680

0.630

0.596

0.675

0.621

0.581

0.686

0.635

0.600

0.681

0.627

0.586

185

19/3.50

0.543

0.537

0.516

0.507

0.552

0.546

0.530

0.520

0.563

0.555

0.543

0.533

0.566

0.559

0.547

0.537




2= 1.155.

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S E C T I O N 5 S H O R T - C I R C U I T P E R F O R M A N C E

5.1 GENERAL

This Section is applicable to the short-circuit maximum temperature rating of electric cables having a rated voltage not exceeding 0.6/1 kV. Guidance is given on the following aspects:

(a) Maximum permissible short-circuit temperatures for cable—

(i) insulating materials;

(ii) outer jacket and bedding materials; and

(iii) conductor and metallic sheath materials and components.

(b) The influence of the method of installation on the temperature limit.

(c) The calculation of the permissible short-circuit current in the current-carrying components of the cable.

5.2 FACTORS GOVERNING THE APPLICATION OF THE TEMPERATURE

LIMITS

The short-circuit temperatures given in Clause 5.5 are the actual temperatures of the current-carrying component as limited by the adjacent materials in the cable and are valid for short-circuit durations of up to 5 s. These temperatures will only be obtained in practice if non-adiabatic heating is assumed (that is, an appropriate allowance for heat loss into the dielectric during the short circuit is made) when calculating the allowable short-circuit current for a given time (not longer than 5 s). The use of the adiabatic method (that is, when heat loss from the current-carrying component during the short circuit is neglected) gives short-circuit currents that are on the safe side. The 5-second period quoted is the limit for the temperatures quoted to be valid, not for the application of the adiabatic calculation method. The time limit for the use of the adiabatic method has a different definition, being a function of both the short-circuit duration and the cross-sectional area of the current-carrying component.

For thermoplastic insulating materials the limits must be applied with caution when the cables are either directly buried or securely clamped when in air. Local pressure due to clamping or the use of an installation radius less than 8 times the cable outside diameter, especially for cables that are rigidly restrained, can lead to high deforming forces under short-circuit conditions. Where these conditions cannot be avoided it is suggested that the limit be reduced by 10°C. The limits quoted are based on average hardness grades of PVC and some adjustment may be necessary for other grades, especially those compounded for improved low-temperature properties.

NOTES:

1 Caution should be exercised when using the limits recommended for thermosetting materials

on large conductors because the high mechanical forces combined with any residual

characteristics could result in deformation sufficient to cause failure.

2 Caution may be needed with total cross-sectional areas in the region of 1000 mm2 when using

the conductor temperatures specified for impregnated paper, cross-linked polyethylene

(XLPE) and ethylene propylene rubber (EPR) insulation and the cable is sheathed with a

lower-temperature material.

3 Information on the short-circuit performance of MIMS cable is not included in this Standard

and reference should be made to manufacturer’s recommendations.

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5.3 CALCULATION OF PERMISSIBLE SHORT-CIRCUIT CURRENTS

The following adiabatic method, which neglects heat loss, is accurate enough for calculating permissible conductor and metallic sheath short-circuit currents for the majority of practical cases and any error is on the safe side. However, for thin screens the adiabatic method indicates much higher temperature rises than actually occur in practice and thus must be used with some discretion.

The generalized form of the adiabatic temperature rise equation, which is applicable to any starting temperature, is as follows:

I2t = K2S2 . . . 5.3(1)

where

I = short-circuit current (r.m.s. over duration), in amperes

t = duration of short circuit, in seconds

K = constant depending on the material of the current-carrying component, the initial temperature and the final temperature

NOTE: Refer to Table 52 for values of constant (K).

S = cross-sectional area of the current-carrying component, in square millimetres.

NOTE: For conductors and metallic sheaths, it is sufficient to take the nominal

cross-sectional area but in the case of screens, this quantity requires careful consideration.

TABLE 52

VALUES OF CONSTANT K FOR DETERMINATION OF PERMISSIBLE

SHORT-CIRCUIT CURRENTS

Constant (K)

Initial

temperature

of conductor

°C

Final temperature of conductor, °C

Copper Aluminium Lead Steel

140 150 160 220 250 350 140 150 160 250 150 200 150 200

130

125

110

37.2

45.7

65.3

52.2

58.6

74.9

63.6

68.9

83.2

106

109

119

121

123

132

155

158

164

24.6

30.2

43.2

34.5

38.7

49.5

42.0

45.5

55.0

79.6

81.5

87.1

9.5

10.7

13.7

17.3

17.9

19.9

18.9

21.2

27.1

34.1

35.4

39.3

90

85

80

85.6

90.1

94.4

93.1

97.3

101

99.9

104

108

131

134

137

143

146

149

173

176

178

56.6

59.5

62.4

61.5

64.3

67.0

66.0

68.6

71.1

94.5

96.3

98.1

17.0

17.8

18.5

22.3

22.9

23.5

33.7

35.2

36.7

44.1

45.3

46.4

75

70

65

98.7

103

107

105

109

113

111

115

119

140

143

146

151

154

157

180

182

185

65.2

68.0

70.7

69.6

72.2

74.7

73.6

76.0

78.4

99.9

102

104

19.2

19.9

20.6

24.0

24.6

25.2

38.2

39.6

41.0

47.6

48.8

49.9

60

55

50

111

115

118

117

120

124

122

126

129

149

152

155

159

162

165

187

189

192

73.3

75.8

78.4

77.2

79.6

82.0

80.8

83.1

85.5

105

107

109

21.3

22.0

22.7

25.7

26.3

26.9

42.4

43.7

45.1

51.0

52.2

53.3

45

40

35

122

126

130

128

131

135

133

136

140

158

160

163

168

170

173

194

196

199

80.9

83.3

85.8

84.4

86.8

89.1

87.7

90.0

92.3

111

113

114

23.3

24.0

24.6

27.4

28.0

28.5

46.4

47.7

49.1

54.4

55.6

56.7

30

25

133

137

138

142

143

146

166

169

176

179

201

204

88.2

90.6

91.5

93.8

94.5

96.8

116

118

25.3

25.9

29.1

29.6

50.4

51.7

57.8

59.0

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5.4 INFLUENCE OF METHOD OF INSTALLATION

When it is intended to make full use of the short-circuit limits of a cable, consideration should be given to the influence of the method of installation. An important aspect concerns the extent and nature of the mechanical restraint imposed on the cable. Longitudinal expansion of a cable during a short circuit can be significant and when this expansion is restrained the resultant forces are considerable.

Where cables are installed in air, provision should be made so that expansion may be absorbed uniformly along the length by snaking rather than permitting it to be relieved by excessive movement at a few points only. Fixings should be spaced sufficiently far apart to permit lateral movement of multicore cables or groups of single-core cables.

Where cables are buried directly in the ground, or must be restrained by frequent fixing, provision should be made to accommodate the resulting longitudinal forces on terminations and joint boxes. Sharp bends should be avoided because the longitudinal forces are translated into radial pressures at bends in the cable route and these may damage thermoplastic components of the cable such as insulation and sheaths. Attention is drawn to the minimum bending radius recommended for the type of cable. For cables in air, it is also desirable to avoid fixings at a bend, which may cause local pressure on the cable.

In determining the short-circuit stresses that will be imposed on a cable, the characteristics of the protective devices used shall be considered.

5.5 MAXIMUM PERMISSIBLE SHORT-CIRCUIT TEMPERATURES

5.5.1 General

Taking into account the recommendation given in Clause 5.2, the temperature values given in Tables 52 to 54 are—

(a) the actual temperatures of the current-carrying components; and

(b) the limits specified for short-circuits of up to 5 s duration.

5.5.2 Insulating materials

The temperature limits given in Table 53 are for all types of conditions when the insulating materials specified are in contact with conductors.

TABLE 53

TEMPERATURE LIMITS FOR INSULATING

MATERIALS IN CONTACT WITH CONDUCTORS

Material Temperature limit

°C

Thermoplastic: LLDPE, PE, V-75, HFI-75-TP, TPE-75,

V-90, HFI-90-TP, TP 90 and V-90HT

—up to and including 300 mm2 160

—greater than 300 mm2 140

Cross-linked elastomeric: R-EP-90, R-CPE-90, R-HF-90,

R-CSP-90, R-HF-110, and R-E-110 250

Cross-linked polyolefin: X-90, X-90UV, X-HF-90 and

X-HF-110

250

High temperature: R-S-150 and Type 150 fibrous 350

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5.5.3 Outer sheath and bedding materials

The temperature limits given in Table 54 are for the outer sheath and bedding materials comprising a continuous screen/sheath or a complete layer of armour wires. These temperatures are for materials where there are no electrical or other requirements necessary, i.e. screen/sheath/armour temperature limits when in contact with the outer sheath materials but thermally separated from the insulation by layers of suitable material of sufficient thickness. If thermal separation is not provided, the temperature limits of the insulation should be used if it is lower than that of the sheath.

TABLE 54

TEMPERATURE LIMITS FOR OUTER SHEATH

AND BEDDING MATERIALS

Material Temperature limit

°C

Thermoplastic 200

Polyethylene 150

High density polyetheylene 180

Polychloroprene, chlorosuphonated

polyethylene and similar 200

5.5.4 Conductor and metallic sheath materials and components

The temperature limits specified in Table 55 apply to the conductor and metallic sheath materials and components.

NOTE: Limitations of materials in contact with these metals should also be considered.

TABLE 55

TEMPERATURE LIMITS FOR CONDUCTOR AND METALLIC SHEATH

MATERIALS AND COMPONENTS

Metals Condition Temperature limit

°C

Copper and aluminium Conductor only*

Welded joint

†

†

Exothermic welded joint

Soldered joint

Compression (mechanical deformation) joint

Mechanical (bolted) joint

250‡

160

250‡

§

Lead

Lead alloy

Steel

170

200

†

* Includes concentric neutral conductors.

† Limited by the material with which it is in contact.

‡ Temperature of adjacent conductor, actual joint will be at a lower temperature.

§ Refer to manufacturer’s recommendations.

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APPENDIX A

EXAMPLES OF THE SELECTION OF CABLES TO SATISFY CURRENT-CARRYING CAPACITY, VOLTAGE DROP AND

SHORT-CIRCUIT PERFORMANCE REQUIREMENTS

(Informative)

A1 EXAMPLE 1

A1.1 Problem

An underground 1500 A three-phase circuit is to be made up of parallel circuits of 400 mm2 V-75 single-core insulated and sheathed copper cables. Determine the minimum number of active conductors required for each of the following forms of installation:

(a) All cables in one conduit or duct.

(b) Each parallel circuit comprising three cables in one conduit or duct.

(c) Each parallel circuit comprising a trefoil group of single-way underground ducts.

(d) Each parallel circuit comprising a trefoil group of three cables buried direct.

A1.2 Solution

Assuming that the conditions specified in Clause 3.4 apply, i.e. soil ambient temperature, thermal resistivity and depth of laying, the following methods would satisfy the load requirements, if the voltage drop is acceptable:

(a) Method A—Single conduit or duct Current-carrying capacity of single 400 mm2 circuit = 492 A (Table 7, Column 24).

From the derating factors of Table 22, which vary according to the number of enclosed circuits, it can be shown that five parallel circuits of 400 mm2 conductors, as illustrated, are required.

The current-carrying capacity of the arrangement is—

492 × 5 × 0.6 = 1476 A

(b) Method B—Groups of conduits or ducts Current-carrying capacity of single 400 mm2 circuit = 492 A (Table 7, Column 24).

From the derating factors of Table 26(2) for groups of underground enclosures, it can be shown that four conduits or ducts, each containing a circuit of 400 mm2 conductors and touching, as illustrated, are required.

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492 × 4 × 0.79 = 1554.7

(c) Method C—Trefoil groups of single-way underground ducts

Current-carrying capacity of single 400 mm2 circuit = 553 A (Table 7, Column 27).

From the derating factors of Table 26(1) for groups of underground enclosures, it can be shown that four trefoil groups of single-way underground ducts, each group representing a circuit of 400 mm2 conductors, as illustrated, are required.

The current-carrying capacity of the arrangement—

553 × 4 × 0.74 = 1636.9 A

(d) Method D—Trefoil groups of cable buried direct Current-carrying capacity of single 400 mm2 circuit = 593 A (Table 7, Column 22).

From the derating factors of Table 25(1) for groups of single-core cables buried direct, it can be shown that three trefoil groups of single-core cables, each group representing a circuit of 400 mm2 conductors and spaced apart, as illustrated, are required.


593 × 3 × 0.87 = 1547.7 A

A1.3 Comparison of different methods

Each of the four methods of installation described in Paragraph A1.2 provide a satisfactory solution to the circuit design problem where the number of 400 mm2 active conductors are to be kept to a minimum for a given installation method. However, in doing so the following factors that may determine the system to be selected are highlighted:

(a) Number of cables Method A leads to the largest number of cables.

(b) Number of enclosures Method C requires twelve enclosures (excluding neutral) whilst Method D requires none.

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(c) Size of enclosures The enclosures in Method C need only be sufficient to accommodate one conductor. However, the single enclosure in Method A will need to be considerably larger.

(d) Size of excavated trench Methods A, B and C require relatively small trench widths in comparison to Method D.

(e) Provision for additional load Methods A, B and C have provision for a further load increase of between 150 and 250 A. Method D would be operating at near maximum load.

The relative importance of these different factors for a particular installation will, in general, determine the cable arrangement selected.

A2 EXAMPLE 2

A2.1 Problem

If 12 loaded single-core conductors are run through a wiring enclosure what derating factor should be applied?

A2.2 Solution

The applicable derating factors could be determined from Table 22. If it is a three-phase circuit, then 12/3 is 4 groups, i.e. 4 circuits, and a derating factor of 0.65 could be applied. If the circuits are single-phase, there would be 6 circuits and therefore a derating factor of 0.57 could be applied.

Applying these derating factors for, say, V-75 insulated 4 mm2 conductors, from Table 7 a three-phase current-carrying capacity is 28 A while the single-phase value from Table 4 is 32 A.

Using the three-phase approach, 28 × 0.65 = 18.2 A.

Using the single-phase approach, 32 × 0.57 = 18.2 A.

Note that these methods result in approximately the same answer.

A3 EXAMPLE 3

A3.1 Problem

A three-phase circuit is to supply a load of 125 A per phase. It is proposed to use two V-75 insulated and sheathed four-core cables bunched together on a surface in a confined ceiling space where the ambient air temperature is 50°C.

Determine—

(a) the minimum conductor size; and

(b) the maximum route length of the circuit if a voltage drop of 3% is permitted on the circuit;

for both aluminium and copper conductors.

A3.2 Solution

The solution is as follows:

(a) Minimum cable size:

Derating factor for bunching = 0.8 (Table 22, Column 5)

Derating factor for 50°C ambient = 0.82 (Table 27(1), Column 9)

Minimum current-carrying capacity of two parallel cables—

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A 190.5 = 0.82

1x

0.8

1x 125

or 95.25 A per cable.

From Columns 5, 6 and 7 of Table 13, the minimum size of the two cables making up the circuit are—

Aluminium—50 mm2

Copper—35 mm2

(b) Maximum route length:

With the same length and disposition of the two cables throughout the circuit, balanced current flow between the parallel cables can be expected.

Assuming worst case conditions of cable operating temperature and load power factor, the simplified method of Clause 4.2 may be used to determine the maximum route length of the circuit (L), in metres, by substitution of the 62.5 A load current for each cable and 3 % (12.45 V) permissible voltage drop in the following equation:

V

VL

c

d

x I

x 1000 =

The values of Vc are obtained from Table 42 for copper and Table 45 for aluminium and result in the following maximum route lengths:

Aluminium m 146.5 = 1.36x 62.5

12.45x 1000

Copper m 179.5 = 1.11x 62.5

12.45x 1000

A4 EXAMPLE 4

A4.1 Problem

Six four-core V-75 insulated and sheathed copper cables are arranged touching in a single horizontal row on a perforated cable tray for the supply of six identical 22 kW motors which have a full-load current of 45 A per phase and are installed at distances of 40 m, 55 m, 90 m, 135 m, 180 m and 225 m from the origin of the cable tray. Determine the minimum conductor size if a voltage drop of 2.4 % (10 V) is permitted for each cable.

A4.2 Solution

The selection of conductor size in this instance must satisfy both the current-carrying capacity requirement, including the effect of the cables being grouped, and the voltage drop limitation.

The cable sizes required to satisfy the voltage drop restriction are assessed using the formula of Clause 4.2, the actual load current of 45 A, the permissible voltage drop, Vd, of 10 V and the three-phase voltage drop figures of Table 42. The results of these calculations, the current-carrying capacity given in Table 13 and its ratio to the load current, are as follows:

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Cable Length Maximum

Fc

Minimum cable

size

Maximum current-

carrying capacity

Ratio of actual load

current to max.

current-carrying

capacity of cable

m mV/A.m mm2 A

A

B

C

40

55

90

5.56

4.04

2.47

10

10

16

51

51

68

0.88

0.88

0.66

D

E

F

135

180

225

1.65

1.23

0.98

25

35

50

91

110

135

0.49

0.41

0.33

Because of voltage drop limitations, cables C to F are substantially larger than required to meet the maximum current-carrying capacity requirements. As a result the contribution of these cables to the effects of mutual heating will be small, in the case of cables E and F, almost negligible.

An examination of the derating factors for groups of multicore cables on perforated trays given in Table 24 would indicate that a factor of 0.76 (Column 9) would apply if all six cables in the group were loaded to achieve the same conductor temperature. Although these conditions do not exist for all cables in this example, the application of this factor will give a conservative but practical solution, as follows:

Minimum current-carrying capacity required of cables = A 59.2 = 0.76

1x 45

Minimum cable size = 16 mm2 (Table 13, Column 5)

As expected, only cables A and B are affected and therefore the recommended minimum cable sizes for the cables A, B, C, D, E and F will be 16 mm2, 16 mm2, 16 mm2, 25 mm2, 35 mm2 and 50 mm2 respectively.

NOTE: The actual derating factor in this situation may be closer to 0.82, the derating factor for

three cables on a tray, which allows for restricted ventilation to cables nested in the middle of

others. Alternative arrangements of the cables, e.g. spacing cables A and B, which operate at a

higher temperature, away from each other and others in the group, may also give rise to less

onerous derating factors and smaller cable sizes.

A5 EXAMPLE 5

A5.1 Problem

Five single-phase circuits of two-core flat V-75 insulated and sheathed cables are fixed to a wall. Where the continuous loading of the cables is assessed as 16, 20, 25, 32, and 40 A, determine the minimum cable sizes required where the cables are in one of the following conditions:

(a) Condition A—spaced apart in a single layer in accordance with Clause 3.5.2.2(c) and Figure 1.

(b) Condition B—spaced apart in a single layer by a distance of one cable diameter between adjacent cables.

(c) Condition C—touching in a single layer.

(d) Condition D—bunched together.

A5.2 Solution


(a) For installation condition A to avoid derating because of grouping, Clause 3.5.2.2(c) and Figure 1 require a minimum vertical spacing between adjacent cables 6 times the diameter of the largest cable in the group. A

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(b) For condition B, the derating factor = 0.90 (Table 22, Column 8)

(c) For condition C, the derating factor = 0.73 (Table 22, Column 8)

(d) For condition D, the derating factor = 0.60 (Table 22, Column 8)

The minimum conductor sizes determined from Column 5 of Table 13 are as follows:

Load Cable size, mm2

A

Spaced 6

diameters

Spaced 1

diameter

Touching single

layer

Bunched

16

20

25

1.5

2.5

2.5

1.5

2.5

4

2.5

4

4

2.5

4

6

32

40

4

6

6

6

6

10

10

16

A6 EXAMPLE 6

A6.1 Problem

A single-phase circuit comprises two 16 mm2 copper single-core sheathed cables with V-75 insulation installed unenclosed on a wall for the supply of a 55 A resistive load.

Determine which single-phase voltage drop values will apply when the cable is operating in—

(a) an ambient air temperature of 40°C; or

(b) an ambient air temperature of 25°C

A6.2 Solution

From Table 4 it will be noted that the cable current-carrying capacity of this configuration is 72 A in an ambient air temperature of 40°C. Equation 4.4(1) may therefore be solved directly for cable operating temperature (θ0) where the ambient air temperature is 40°C but requires some correction to the rated current (IR) before application to an ambient air temperature of 25°C. Appropriate calculations are as follows:

(a) Ambient air temperature 40°C

40 75

40 =

72

55 0

2

−−θ

⎟⎠

⎞⎜⎝

⎛

θ0 = 60.4°C, say 60°C

The three-phase voltage drop for this cable configuration and operating temperature obtained from Table 41 is 2.32 mV/A.m. The single-phase value is then determined in accordance with Clause 4.3.3(a).

Single-phase voltage drop value = 1.155 × 2.32

= 2.68 mV/A.m.

(b) Ambient air temperature 25°C The correction factor for operation in a 25°C ambient air temperature is used to determine the maximum current that will give rise to the maximum operating temperature of 75°C.

Correction factor = 1.21 (from Table 27)

25 75

25 =

21.172

55 0

2

−−θ

⎟⎟⎠

⎞⎜⎜⎝

⎛

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θ0 = 44.9°C, say 45°C

The three-phase voltage drop for this cable configuration and operating temperature obtained from Table 41 is 2.20 mV/A.m. The single-phase value is then determined in accordance with Clause 4.3.3(a)—

Single-phase voltage drop value = 1.155 × 2.20

= 2.54 mV/A.m.

A7 EXAMPLE 7

A7.1 Problem

A three-phase circuit comprises 3 × 150 mm2 single-core copper V-75 sheathed active conductors and a 1 × 70 mm2 single-core copper V-75 sheathed neutral conductor bunched together in free air. Assuming an ambient air temperature of 40°C and the same length of 150 m for all conductors, determine the maximum voltage drop when the magnitude and phase angle of the currents in the respective active conductors are as follows:

IA = 195 /0°

IB = 300 /120°

IC = 230 /240°

A7.2 Solution

It is not necessary in this example to take into account the load power factor as the maximum voltage drop conditions are assumed where load power factor and cable power factor are equal. The voltage drop in each cable will then be equal to ILZc.

The 300 A load current in phase B is, according to Table 7, close to the maximum permissible for such an arrangement and consequently the conductor operating temperature may be assessed as 75° for the application of Table 40 corresponding to a three-phase voltage drop of 0.305 mV/A.m.

The voltage drop on phase B conductor alone is therefore—

VdB = IBLBZcB

= 300 /120° × 150 × 1000

1

3

305.0 ×

= 7.924 /120°

The current flowing in the neutral is determined from the relationship—

IA + IB + IC + IN = 0

IA + IB + IC = 195 /0° + 300 /120° + 230 /240°

= 195 + (−150 + j259.8) + (−115 − j199.2)A

= −70 + j60.6

∴ IN = 70 − j60.6

= 92.6 /−40°.9°A

The operating temperature of the neutral may then be determined in accordance with Clause 4.4 and the rated figure given in Table 7, i.e.

4075

40

185

6.92 0

2

−−θ

=⎟⎠

⎞⎜⎝

⎛

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θ0 = 49°C, say 60°C allowing for contact with conductors operating at higher temperatures.

From Table 40 and a conductor temperature of 60°C the three-phase voltage drop is given as 0.563 mV/A.m.

The voltage drop on the neutral conductor alone is therefore—

VdN = INLNZcN

= 92. 6 /−40.9°V × 150 × 1000

1

3

0.563 ×

= 4.515 /−40.9°V

The maximum single-phase voltage drop is therefore—

Vd = VdB − VdN = 7.924 /120° − 4.515 /−40.9°

= −3.962 + j7.862 − 3.413 + j2.956

= −7.375 + j9.818

= 12.28 /120.9 V

A8 EXAMPLE 8

A8.1 Problem

Select the minimum size conductor based on thermal consideration, for a copper cable with compression joints connected to a supply where protection is provided by an air circuit-breaker with a clearance time of 1 s and a breaking capacity of 10 kA.

Calculate the minimum conductor size for the following two types of cable:

(a) PVC insulated.

(b) XLPE insulated.

A8.2 Solution


(a) PVC insulated

(i) To find the value of constant (K) the initial conductor temperature and the final conductor temperature must be known.

For PVC it is assumed that the initial operating temperature is 75°C (for V-75, V-90 and V-90HT). From Table 53, and assuming that the cable is smaller than 300 mm2, the final operating temperature can be selected as 160°C. From Table 52 the value of K can be selected as 111 for a copper conductor.

(ii) As the circuit-breaker protecting the circuit is rated at 10 kA breaking capacity, we can assume a value of 10 000 A for I.

(iii) As the clearance time of the circuit-breaker is 1 s, it can be assumed that the value of t, which is the total time the fault current is flowing, is also 1 s.

(iv) Rearranging Equation 5.3(1) we get—

S = ⎟⎟

⎠

⎞

⎜⎜

⎝

⎛2

2

K

tI

Substituting the values for I, t and K, the minimum cross-section area is calculated as—

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S = ⎥⎥⎦

⎤

⎢⎢⎣

⎡ ×2

2

)111(

1)00010(

= 90.1mm2

Therefore, the minimum cable size would be 95 mm2.

(b) XLPE insulation

Using the same process as in Item (a) the following steps are taken:

(i) Initial operating temperature for X-90 insulation (assumed maximum) ....... 90°C

Final operating temperature from X-90 insulation (from Table 53) ........... 250°C

Value of constant (K) from Table 52 .............................................................143

(ii) Value of short-circuit current (I) .......................................................... 10 000 A

(iii) Value of time (t) is ......................................................................................... 1 s

S = ⎟⎟

⎠

⎞

⎜⎜

⎝

⎛2

2

K

tI

2 = ⎥⎦

⎤⎢⎣

⎡ ×2

2

)143(

1)00010(

= 69.9 mm2

Therefore, the minimum cable size would be 70 mm2.

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APPENDIX B

LIST OF TABLES

(Informative)

Table Title Page

1 Limiting temperatures for insulated cables 14

2 Reduction factors for harmonic currents in 4- and 5-core cables 27

3(1) Schedule of installation methods for cables deemed to have the same current-carrying capacity and

cross-references to applicable derating tables—Unenclosed in air

28


cross-references to applicable derating tables—Enclosed

30


cross-references to applicable derating tables—Buried direct in the ground

32


cross-references to applicable derating tables—Underground wiring enclosures

33

4 Current-carrying capacities

Cable type: Two single-core

Insulation type: Thermoplastic

34



Insulation types: X-90, X-HF-90, R-EP-90, R-CPE-90 or R-CSP-90

37



Insulation types: R-HF-110, R-E-110 or X-HF-110

40


Cable type: Three single-core


42




45




48


Cable type: Two-core sheathed


50




53




56


Cable types: Three-core and four-core


58


Cable types: Three-core and four-core


61

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Table Title Page


Cable types: Three-core and four-core sheathed


64


Cable type: Flexible cords

Insulation types: Thermoplastic or cross-linked

66


Cable types: Cables and flexible cords

Insulation types: R-S-150, Type 150 fibrous or 150°C rated fluoropolymer

67


Cable type: Bare single-core MIMS cables with copper conductors

68


Cable type: Bare multicore MIMS cables with copper conductors

69


Cable types: Aerial cables with copper conductors

70


Cable types: Aerial cables with aluminium conductors

72

22 Derating factors for bunched circuits

Cable types: Single-core and multicore

Installation conditions: In air or in wiring enclosures

74

23 Derating factors for circuits

Cable type: Single-core

Installation conditions: In trays, racks, cleats or other supports in air

75

24 Derating factors for circuits

Cable type: Multicore

Installation conditions: In trays, racks, cleats or other supports in air

77

25(1) Derating factors for groups of circuits


Installation conditions: Buried direct in ground

79


Cable type: Multicore


80



Installation conditions: In underground wiring enclosures—Enclosed separately

81


Cable types: Single-core or multicore

Installation conditions: In underground wiring enclosures—Multicore cables enclosed separately or

more than one single-core cable per wiring enclosure

82

27(1) Rating factors

Variance: Air and concrete slab ambient temperatures

Installation conditions: Cables in air or heated concrete slabs

83


Variance: Soil ambient temperatures

Installation conditions: Cables buried direct in ground or in underground wiring enclosures

83



Variance: Depth of laying


84



Variance: Depth of laying

Installation conditions: In underground wiring enclosures

84

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Table Title Page

29 Rating factors

Variance: Thermal resistivity of the soil (from 1.2°C.m/W)

Installation conditions: Buried direct in ground and in underground wiring enclosures

85

30 Reactance at 50 Hz

Cable type: All cables excluding flexible cords, flexible cables, MIMS cables and aerial cables

92


Cable types: Flexible cords and flexible cables

93


Cable type: MIMS

94


Cable type: Single-core aerial with bare or insulated conductors

95

34 a.c. resistance at 50 Hz


96


Cable type: Multicore with circular conductors

97


Cable type: Multicore with shaped conductors

97


Cable types: Flexible cords and flexible cables with copper conductors

98


Cable type: MIMS

99


Cable type: Single-core aerial with bare or insulated conductors

100

40 Three-phase voltage drop (Vc) at 50 Hz

Cable types: Single-core insulated and sheathed copper conductors laid in trefoil

101


Cable types: Single-core insulated and sheathed copper conductors, laid flat touching or in a wiring

enclosure

102


Cable type: Multicore with circular copper conductors

103


Cable types: Single-core insulated and sheathed aluminium conductors, laid in trefoil

104


Cable types: Single-core insulated and sheathed aluminium conductors, laid flat touching

105


Cable type: Multicore cables with circular aluminium conductors

106


Cable types: Single-core flexible cords and flexible cables, laid in trefoil

107


Cable types: Single-core flexible cords and flexible cables, laid flat touching or in a wiring enclosure

112


Cable types: Multicore flexible cords and flexible cables

109


Cable types: Single-core and multicore MIMS, laid in trefoil

110


Cable type: Aerial with bare or insulated copper conductors

111


Cable type: Aerial with bare or insulated aluminium conductors

112

52 Values of constant K for determination of permissible short-circuit currents 114

53 Temperature limits for insulating materials in contact with conductors 115

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Table Title Page

54 Temperature limits for outer sheath and bedding materials 116

55 Temperature limits for conductor and metallic sheath materials and components 116

D1 Load current sharing and low magnetic field configurations 131

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APPENDIX C

EXAMPLES OF THE APPLICATION OF REDUCTION FACTORS FOR

HARMONIC CURRENTS

(Informative)

Consider a three-phase circuit with a design load of 35 A to be installed using four-core PVC insulated cable clipped to a wall.

From Table 13, a 6 mm2 cable with copper conductors has a current-carrying capacity of 37 A and hence is suitable if harmonics are not present in the circuit.

If 20% third harmonic is present then a reduction factor of 0.86 is applied and the design load becomes:

A410.86

35 =

For this load a 10 mm2 cable is suitable.

If 44% third harmonic is present the cable size selection is based on the neutral current which is:

A46.230.4435 =××

and a reduction factor of 0.86 is applied, leading to a design load of:

A53.70.86

46.2 =

For this load, a 16 mm2 cable is suitable.

If 50% third harmonic is present the cable size is again selected on the basis of the neutral current, which is:

A52.530.535 =××

In this case, the reduction factor is 1 and a 16 mm2 cable is suitable.

All the above cable selections are based on the current-carrying capacity of the cable only. Voltage drop and other aspects of design have not been considered.

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131 AS/NZS 3008.1.1:2009

COPYRIGHT

APPENDIX D

RECOMMENDED CIRCUIT CONFIGURATIONS FOR THE INSTALLATION OF

SINGLE-CORE CABLES IN PARALLEL

(Informative)

TABLE D1

LOAD CURRENT SHARING CONFIGURATION

Mode Two-phase Three-phase

Two

conductors

per phase

Three

conductors

per phase

Not recommended

Four

conductors

per phase

NOTES:

1 Neutral conductors are to be located so as to not disturb the symmetry of the groups as illustrated.

2 Non-symmetrical configuration may cause unequal distribution of current between conductors.

Provision should be made to maintain the recommended configurations to avoid these problems.

A1

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AS/NZS 3008.1.1:2009 132

AMENDMENT CONTROL SHEET

AS/NZS 3008.1.1:2009

Amendment No. 1 (2011)

CORRECTION

SUMMARY: This Amendment applies to Clauses 3.3.2 and 4.4, Tables 3(1), 6, 7, 8, 9, 10, 12, 13, 15, 16 and

34, and Appendices A and D.

Published on 15 August 2011.

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Australian/New Zealand Standard · AS/NZS 3008.1.1:2009 This Joint Australian/New Zealand Standard was prepared by Joint Technical Committee EL-001, Wiring Rules. It was approved

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